Thurlby Dsa524 User manual

Thurlby DSA524

digital storage adaptor

OPERATING MANUAL AND TUTORIAL

V2.0

INTRODUCTION

This manual is divided into four sections as follows:

Section 1 is the main reference section which contains a detailed

description of the operation of each function.

Section 2 is a tutorial for new users (or for existing users needing

examples of how functions operate).

The Appendices provide additional detail on some of the more

complex functions and on some of the theoretical aspects of digital

storage.

The Specifications give detailed technical specifications for the

instrument, plus service and warrant details.

N.B. The DSA524 can use either an oscilloscope or a personal

computer (IBM compatible) as the displa device. This manual onl

covers use with an oscilloscope. To use a PC as the displa device

the "DS-PC Link" software package must be purchased, an additional

manual is supplied with this software.

FIRMWARE LEVEL

From time to time small revisions ma be made to the

firmware of the DSA524 (the firmware is the ROM based

program code for the unit).

The firmware level is displa ed briefl whenever the unit is

first switched on (and when SET 'SCOPE is used) as DSA524

X.XX, where X.XX is the firmware level.

This issue of the operating manual applies to units with a

firmware level of 2.71 and above.

IT IS VERY STRONGLY RECOMMENDED THAT NEW

USERS START BY FOLLOWING THE TUTORIAL.

INDEX

Title Section P ge

REFERENCE SECTION

Connecting an Oscilloscope..................................... R1 ...............2

Setting up the Displa .......................................... R2 ...............2

Front Panel Controls ............................................. R3 ...............2

Escape and Reset ................................................ R4 ...............2

Controlling Digitising ............................................ R5 ...............2

Timebase Setting ................................................. R6 ...............2

CH1 and CH2 ....................................................... R7 ...............3

Digitising Memories .............................................. R8 ...............3

Trigger ................................................................ R9 ...............3

Trace A and Trace B ............................................. R10 ..............4

Memor Search (Comp, Scan, Mag) ........................ R11 .............5

Indexed Waveform Memories ................................. R12 ..............5

Displa Update Rate .............................................. R13 .............5

Roll Mode Operation ............................................. R14 .............6

Repeat Mode Operation ......................................... R15 .............6

Cursor Measurement ............................................. R16 .............6

Program Mode ...................................................... R17 .............6

Sine Interpolation ................................................ R18 .............7

Average ............................................................... R19 .............7

AxB (Trace Multipl ) ............................................. R20 .............7

Line or Dots Displa ............................................. R21 .............7

Plot ..................................................................... R22 .............7

Print ................................................................... R23 .............8

Remote Control and Data Transfer ......................... R24 .............8

RS-423 Interface ................................................... R25 ............8

GP-IB (IEEE-488) Interface ................................... R26 ............8

Directl Acting Functions ...................................... R27 ............8

USERS TUTORIAL

Index to Tutorial .......................................................................9

APPENDICES

The Oscilloscope Displa ........................................ Appendix A 16

Aliasing ............................................................... Appendix B 16

Bandwidth and Interpolation .................................. Appendix C 16

Analog Plotter Function ......................................... Appendix D 17

Connecting the Serial Interface .............................. Appendix E 18

Software Commands ............................................. Appendix F 18

SPECIFICATIONS

DSA524 Technical Specifications ............................ S1 ................20

Electrical Isolation ................................................. S2 ...............22

General Safet Considerations ............................... S3 ...............22

Fuse Replacement ................................................ S4 ...............22

Maintenance and Repair ....................................... S5 ...............22

Updating the Firmware ......................................... S6 ...............22

Guarantee ........................................................... S7 ...............22

ADDENDA AND ERRATA .........................................................22

REFERENCE SECTION

R1. CONNECTING AN OSCILLOSCOPE

An conventional oscilloscope with an 8x10 division graticule can

be used with the DSA524. Onl one input channel is needed and

a bandwidth of 5MHz is sufficient. The oscilloscope can be

connected using a single BNC to BNC cable. Alternativel two

cables can be used (see Appendix A).

Connect the rear panel socket marked "composite" to the vertical

input of the oscilloscope. If a two cable connection is preferred,

connect the rear panel socket marked "trigger" to the external

trigger input of the oscilloscope.

Set up the oscilloscope controls as follows:-

Vertic l Input: DC coupling

100mV per division

Timeb se: 50usec per division

No Sweep Hold-off

Trigger: Source — as input channel (single

cable connection)

— or external (two cable

connection)

Mode — normal (not bright-line auto)

Coupling — AC

Slope — negative

Level — negative

R2. SETTING UP THE OSCILLOSCOPE DISPLAY

Switch on the DSA524 (the power switch is at the rear) and wait

while the unit performs a brief selftest and initialisation. The

oscilloscope should then show a message as follows:-

"CENTRE ARROW TIP" alternating with "THEN PRESS ESCAPE"

Adjust the oscilloscope's horizontal and vertical position controls

until the tip of the arrow is exactl in the centre of the screen.

Two horizontal lines should be visible, one at three divisions

above the graticule centre and one at three divisions below.

Pressing the ESCAPE ke on the DSA524 (top right-hand corner)

will remove this set-up displa and start normal operation.

Once the displa oscilloscope has been set up, no further use

need be made of its controls except for occasional re-centering of

the trace to correct for an warm-up drift. To re-centre the trace

press the two ke s marked "SET 'SCOPE" (on the lower right of

the DSA) and adjust the oscilloscope's position controls to centre

the arrow tip. If problems occur when setting up the displa read

Appendix A.

The oscilloscope setup

displa .

R3. FRONT PANEL CONTROLS

All of the controls, including the rotar ones, are monitored b a

microprocessor which then performs the control. All of the

switches are of a momentar non-latching "ke " t pe whose

status is indicated either b lamps under the panel or, where

appropriate, b text on the displa . Each rotar control is enabled

or disabled b the ke to its right. The control is enabled when

the lamp above the ke is off, and is disabled when the lamp is

on.

The ke s within the numeric ke pad section (right-hand side of

unit) have up to three functions. The normal function is printed

in black above each ke . After the SHIFT control is pressed the

function becomes as printed in green above the ke . When a

function ending in (NN) is pressed (e.g. SAVE(NN)) the ke will

enter the number printed alongside it.

Note that when SHIFT or a function ending in (NN) is pressed,

the lamp marked ENTER will flash to indicate that one or more

further ke presses is required. An function that causes the

ENTER lamp to flash can be cancelled b pressing that function

ke again.

Note that some of the functions (including SET 'SCOPE)

automaticall set the RUN/HOLD function to HOLD. If digitising

ceases unexpectedl check to see if ou have unintentionall

set RUN/HOLD to HOLD.

All of the front panel settings are retained when the power is

turned off (except for RUN/HOLD which is alwa s set to HOLD

at power-on).

R4. ESCAPE AND RESET

The ESCAPE ke is used to terminate some of the functions of

the DSA such as "SET PLOT" and "SET AVG". At other times it

has no effect except after SHIFT has been pressed.

Pressing SHIFT followed b ESCAPE gives the RESET function.

RESET places the DSA into a known state. It cancels all of the

more complex functions and sets the DSA into a state which

makes it eas to displa the input signals.

The main effect of RESET is to set up the unit as follows:-

RUN /HOLD RUN.

CH1 and CH2 Coupling: AC, Volts/div: 1V, Offset: ZERO,

On/off: ON.

TRIGGER Run/hold: RUN, Source: CH1, Mode: AUTO,

Level: ZERO, Slope: POS, Coupling: AC.

TRACES A Trace A source: CH1, Trace B source: CH2,

and B Gain variable: CAL, Position: HOME.

TIMEBASE Time/div: 20usec.

ALL OTHER

FUNCTIONS OFF.

After pressing RESET the DSA will be set such that the CH1

signal is displa ed on trace A and the CH2 signal on trace B.

The displa will be updated about three times per second. The

input sensitivit will be set at 1V per division. The timebase will

be set to 20usec/div. The input sensitivit and timebase speed

will need to be adjusted to suit the signal.

R5. CONTROLLING DIGITISING (DATA ACQUISITION)

The digitising of the input signals is controlled b the two ke s

at the top of the TRIG section marked RUN/HOLD and SINGLE.

When RUN/HOLD is set to RUN, the DSA is automaticall re-

armed following each acquisition. Thus digitising is repeated

continuousl provided that triggering is active (see Section R9

Trigger — Mode).

When RUN/HOLD is set to HOLD, digitising is stopped and the

contents of the digitising memories is frozen. When set to

HOLD, the DSA can be armed for a single acquisition using the

SINGLE ke .

Digitising can be performed on both input signals

simultaneousl , or on either signal individuall . Each input

channel (CH1 and CH2) is enabled or disabled using the ke

marked ON/OFF at the top of each channel section. When one

of the input channels is turned off, the digitising memor

associated with that channel is frozen and digitising takes place

on the other channel alone.

R6. SETTING THE TIMEBASE

The timebase of the DSA524 is somewhat different from that of

a conventional real-time oscilloscope. The time per division

ke s, instead of setting a sweep speed, actuall control the

sampling rate of the digitiser. The shorter the time per division

the higher the digitising rate. After it has been stored, the

digitised data is displa ed as 1024 samples across the screen

(100 samples per graticule division with 12 samples before and

12 samples after the graticule). Thus the time per division is

equal to 100 divided b the sampling rate.

The timebase should be set in much the same wa as with a real-

time oscilloscope but, unlike a real-time oscilloscope, the effect of

setting the timebase speed to too slow a rate can cause aliasing

effects on the displa (see Appendix B). For this reason if the

signal frequenc is unknown a fast timebase speed should be

selected initiall .

Alternativel , if the signal is repetitive, the AUTOSET facilit can

be used. It is full described at the end of this section.

As well as setting the digitising rate, the time per division ke s

also set the digitising mode. There are three modes:

NORMAL MODE: 100msec to 5usec per division (1KS/s to 20MS /s

sample rates) suitable for single or repetitive events. The screen

is updated after each digitising is completed.

ROLL MODE: 200msec to 200 minutes per division (500S/s to

8.3mS/s sample rate). Suitable for single or repetitive events. The

screen is updated continuousl . As digitising takes place, new

data is written onto the right-hand side of the screen and old

data disappears from the left-hand side. Thus the waveform

appears to "roll" across the screen similarl to a strip chart

recorder. (See Section R14. Roll Mode Operation.)

REPEAT MODE: 2usec to 50nsec per division (50MS/s to 2GS /s

equivalent sample rate). Suitable for repetitive events onl . The

screen is updated more slowl than in normal mode. The signal

must be repetitive and must be generating a trigger signal. Auto

free-run (trigger mode = AUTO) is not available in repeat mode,

neither is LINE trigger. (See Section R15. Repeat Mode

Operation.)

The time per division ke s will autorepeat if held. When a change

in timebase speed causes a mode change a "beep" will be heard.

ROLL and REPEAT (RPT) modes are indicated b front panel

lamps.

When CH1 and CH2 are ON simultaneousl the DSA524 uses a

single high speed digitiser to digitise both signals. For timebase

speeds of 20usecs per division and slower, both signals are

digitised together using a ver high speed chopping technique.

For timebase speeds of 10usecs per division and faster the

signals are digitised separatel on alternate trigger events. The

CHOP and ALT lamps show which mode is being used.

AUTOSET: The autoset function can be used to automaticall set

the timebase speed so as to avoid aliasing effects. The input

signal must be repetitive and be generating a trigger signal

whose repetition rate is between 50Hz and 5MHz.

To initiate autoset press the two ke s in the timebase section

marked AUTOSET simultaneousl . If the trigger rate is between

50Hz and 1MHz the timebase will be reset to a position that gives

between 4 and 10 trigger events across the screen. The AUTO

lamp will illuminate for 3 seconds and the displa will show the

message "AUTOSET SUCCESSFUL" for 3 seconds.

If the trigger rate was below 50Hz the timebase setting will

remain unchanged, the AUTO lamp will not illuminate and the

displa will show the message "TRIGGER RATE TOO LOW" for 3

seconds.

If the trigger rate was above 1MHz the timebase will reset to

1usecs/div, the AUTO lamp will illuminate for 3 seconds, the

displa will show the message "TRIGGER RATE ABOVE 1MHz"

and the DSA will "beep" to indicate that the timebase speed ma

need to be set faster.

R7. CH1 AND CH2

The two input channels are identical. The input sensitivit is

variable between 10V and 2mV per division. The maximum

bandwidth is 35MHz down to 20mV/div, 20MHz at 10mV/div,

10MHz at 5mV/div and 5MHz at 2mV/div. The volts per division

ke s autorepeat if held. The input coupling can be AC ( 3db =

5Hz) or DC.

When both ke s are pressed simultaneousl the unit enters an

AUTORANGING mode whereb the sensitivit is automaticall

set to maintain a peak to peak signal amplitude between 2 and

4 divisions. The AUTO lamp is then illuminated. To leave auto-

ranging mode press either ke . Autoranging does not operate in

"roll" or "repeat" timebase modes.

The digitiser has an input d namic range equivalent to ± 4.25

screen divisions. To maintain the input signal within this range

an OFFSET control is provided which has a range of ±8

divisions. OFFSET can be set to zero b pressing the

ZERO/(VAR) ke . Press it again to return to variable offset.

If the signal goes outside the d namic range of the digitiser

while digitising is taking place the AUTO/OVLD lamp flashes to

show that a signal overload is occurring. Signal values which

exceed the d namic range will be digitised as either + 4.25 divs

or - 4.25 divs. Note that the lamp will continue to flash when

the waveform is "held" even if the signal overload is removed.

The input amplifiers have an automatic s stem for removing

offset errors. If the GND and AC/DC ke s are pressed simultan-

eousl an "autocalibration" takes place which re-checks and

removes offset errors from ever volts/div position. AUTOCAL

should be used when the unit has warmed up, i.e. after about

20 minutes.

Each channel has an ON/OFF ke . The operation of these ke s

is explained in the next section (Digitising Memories).

R8. DIGITISING MEMORIES

Each channel has its own digitising memor of 4K words. When

both channels are turned ON (using the channel ON/OFF ke s),

both memories are updated whenever digitising is performed.

When one channel is turned OFF, the contents of its digitising

memor is frozen and onl the memor for the other channel is

updated.

The contents of the digitising memories is unaffected b the

settings of the trace controls. The digitising memories are non-

volatile i.e. their contents are not destro ed when the power is

turned off.

Note that if either of the digitising memories is storing a wave-

form which gave rise to an overload condition, the OVLD lamp

will continue to flash until the memor is overwritten with a

waveform which is within the d namic range of the digitiser.

R9. TRIGGER

The trigger circuitr of the DSA is broadl similar to that of a

real-time oscilloscope. The trigger signal defines the exact

moment at which digitising takes place. Control of the trigger

circuit defines which part of a waveform will be stored.

Man functions are similar to those of a conventional oscillo-

scope:

SOURCE: Can be from CH1, CH2 or EXT (external

trigger BNC socket).

MODE: AUTO — similar to "Bright Line Auto", the

digitiser free runs if there is no trigger or if the

trigger repetition rate is below 20Hz. If the rate is

above 20Hz digitising takes place in s nchronism.

NORM (Normal) — digitising is alwa s in s n-

chronism with the trigger signal. If there is no

trigger signal digitising stops.

LINE — digitising is in s nchronism with AC line

rate (50 or 60Hz).

N.B. The trigger modes operate differentl when

the timebase is set to "roll" mode (see Section

R14. Roll Mode Operation).

Neither Auto nor Line are available when the

timebase is set to "repeat" mode (see Section

R15. Repeat Mode Operation).

LEVEL: Variable over ±4 divisions. Press ZERO/(VAR)

ke to set zero level triggering, press again to

return to variable.

SLOPE: Can be POS (positive edge triggered) or NEG

(negative edge triggered).

COUPL: Can be AC, DC or HFREJ (high frequenc

reject). With TV and video signals, use AC for Line

s nc and HFREJ for Frame s nc.

N.B. The lamp marked TRIG, to the right of the SINGLE ke ,

indicates the presence of a trigger signal.

Other functions are specific to the digital storage function:

RUN/HOLD: RUN — enables continuous digitising with

s nchronism defined b the trigger mode control.

The previous contents of both digitising memories

are overwritten unless one has alread been frozen

using the channel ON/OFF ke .

HOLD — disables digitising. The contents of both

digitising memories are frozen.

SINGLE: Onl operates when RUN/HOLD is set to

HOLD. Enables a single update of the digitising

memor with s nchronism defined b the trigger

mode control.

EVENTS Sets a number of trigger events (0 to 15) which

DELAY: must occur before a trigger is sent to the digitiser.

This allows dela ed triggering on complex single-event

waveforms, and can be used to avoid mis-triggering of complex

repetitive waveforms (similarl to Sweep Hold-off on a real-time

oscilloscope). Pressing either ke shows the existing value on the

displa for three seconds. Repeated pressing increments or

decrements the number, the ke s auto-repeat if held. To rapidl

turn events dela off (i.e. to 00) press both ke s simultaneousl .

Note that when using AUTO trigger mode, events

dela will increase the minimum frequenc at

which it can be used from 20Hz to (1 + 20Hz,

where n is the number of events.

TIME DELAY: Sets the time dela between the trigger event and

the start of the digitising process. The dela is

measured in screen divisions and can be positive

(POST TRIGGER DELAY) or negative (PRE

TRIGGER DELAY).

POST — this acts similarl to sweep dela on a

real-time oscilloscope. B adding time dela and

then selecting a faster timebase speed, a section of

a waveform occurring long after the trigger event

can be examined. For "normal" mode timebase

speeds (100msec/div to 5usec/div) the number of

divisions of post-trigger dela is automaticall

increased or decreased to maintain a constant time

dela when the timebase speed is changed (within

a limit of 9,999 divisions maximum).

PRE — there is no equivalent to pre-trigger on a

real-time oscilloscope. Pre-trigger allows the part of

the waveform which occurred before the trigger to

be stored and observed. The maximum pre-trigger

dela is —40 divisions.

Pressing either ke shows the existing value of

dela on the screen for three seconds. Repeated

pressing increments or decrements the number,

the ke s autorepeat if held. To rapidl turn time

dela off (i.e. to 0000) press both ke s

simultaneousl .

N.B. Neither pre nor post trigger dela is available

in "repeat" mode. In "roll" mode onl post trigger

dela is available. See Section R14. Roll Mode

Operation for an explanation.

A waveform burst (4

c cles) captured with

no trigger time dela .

The same waveform

burst captured with 4

divisions of post

trigger dela .

The same waveform

burst captured with 9

divisions of pre

trigger dela .

R10. TRACE A AND TRACE B

The DSA524 can displa two traces simultaneousl , the traces

are called A and B. Each trace has its own 1K word memor

which can be loaded with data either from the corresponding

digitising memor (CH1 for trace A or CH2 for trace B) or from

an indexed waveform memor .

The trace controls operate on the waveform after it has been

digitised but before it has been 'displa ed. Therefore the can

be used to modif waveforms recalled from a waveform store

as well as waveforms taken from the digitising memories of the

input channels.

POSITION: Enables the vertical position of the trace on the

displa to be adjusted. Pressing the HOME/(VAR)

ke toggles between fixed position (HOME) and

variable position.

GAIN Enable intermediate sensitivit levels to be set.

VARIABLE: Pressing the CAL/( UNCAL) ke toggles

between calibrated gain (X1) and variable gain

(X1 to X0.2).

CH1 Pressing this ke causes the trace to displa the

(or

CH2): contents of the digitising memor for the

corresponding input channel.

RCL(NN): (Recall indexed waveform memor ). Pressing

this ke followed b a two digit number on the ke pad

causes the trace to displa the contents of the

corresponding waveform memor . It also sets RUN

/HOLD to HOLD.

OFF: Pressing the CH1 (or CH2) and RCL(NN) ke s

simultaneousl turns the trace off (the CH ke should be

pressed first, otherwise RUN/HOLD will be set to HOLD).

INV(Invert): Applies to Trace B onl . Causes the waveform

to be displa ed inverted.

ADD B: Applies to Trace A onl . Displa s the sum of

what is presentl on Trace B and what was

previousl on Trace A.

SAVE(NN): Pressing this ke followed b a two digit number

causes the waveform presentl displa ed on that

trace to be stored in the corresponding waveform

memor . It also sets RUN/HOLD to HOLD.

R11. MEMORY SEARCH (COMP/SCAN/MAG)

Although the size of each trace memor is 1K words (equivalent

to 10.24 divisions across the screen) the size of each digitising

memor is 4K words (equivalent to 40.96 divisions). Normall

each trace memor is filled with the first 1K words from the cor-

responding digitising memor . (Note that in "roll" mode it is the

last 996 words — see Section R14. Roll Mode Operation.)

To enable all of the digitising memor to be viewed, a SEARCH

ke is provided next to the timebase section. Pressing SEARCH

c cles through three states as detailed below. The actual mode is

indicated both b a corresponding front panel lamp and b a

diagram on the displa which remains there for three seconds

after the mode has been changed.

COMP: Compresses all 4K words of the digitising

memor into the 1K words of the trace memor b

transferring ever fourth word.

SCAN: Enables an 1K section of the digitising

memor to be transferred to the trace memor via

a moveable window. The window is moved using

the two ke s marked SCAN/MAG. The position of

the window is shown graphicall on the displa for

three seconds whenever either ke is pressed.

Repeated pressing of either ke moves the window

left or right in one division (100 word) steps. The

ke s autorepeat if held.

MAG: Digitall magnifies an 100 word section of the

trace memor b ten so that it fills the displa . The

section is selected via a moveable window which is

moved using the two ke s marked SCAN/MAG. The

position of the window is shown graphicall on the

displa for three seconds whenever either ke is

pressed. Repeated pressing of the ke moves the

window left or right in half division (50 word)

steps. The ke s autorepeat if held.

A captured waveform

displa ed using Com-

press mode.

The same waveform

displa ed using Scan

mode.

The same waveform

displa ed using

Magnif mode.

To leave SEARCH mode and set the displa mode back to

normal, press the two SCAN/MAG ke s simultaneousl .

If one of the traces is displa ing a waveform recalled from an

indexed waveform memor when SEARCH is selected, the re-

called waveform will remain unaffected.

R12. INDEXED WAVEFORM MEMORIES

The DSA524 has sixteen 1K word memories for temporar or

permanent storage of waveforms. Each memor is identified b

a two digit number from 01 through to 16. The memor is sup-

ported b trickle charged Ni-Cad batteries which will remain

charged for several months should the unit be left unpowered.

To store a waveform in an indexed memor , obtain the required

waveform on the displa and press the SAVE(NN) ke for the

appropriate trace. This will cause the ENTER lamp above the

numeric ke pad to flash. Enter the two digits corresponding to

the required memor position, the displa will show "MEMORY

NN = TRACE A (or B) for 3 secs.

Note that the waveform is stored exactl as it appears on the

displa except for its vertical position which is stored as it would

be if the trace position control was at HOME.

To recall a waveform from an indexed memor , press the

RCLINN) ke for the trace on which the waveform is to be dis-

pla ed. This will cause the ENTER lamp above the numeric ke -

pad to flash. Enter the two digits corresponding to the required

memor , the displa will show "TRACE A (or B) = MEMORY NN"

for 3 secs.

When a waveform recalled from an indexed memor is being

displa ed, the MEM lamp on the corresponding trace will be illu-

minated. The memor number from which it was recalled can

be checked b pressing the RCLINN) ke twice.

An trace recalled from a waveform store is temporaril sup-

pressed when in "roll" mode RUN or SINGLE.

R13. DISPLAY UPDATE RATE

In "normal" mode (timebase speeds between 100msec and

5usec per division) the displa update rate can be varied. This

is done with the ke marked RATE (within the timebase

section).

The default update rate (NORM) re-starts the digitising process

about 300msecs after the completion of the previous one. This

gives a displa update rate of about 3 per second for higher

timebase rates, slowing down as the timebase speed gets into

the tens of milliseconds (at 100msec per division digitising takes

4 seconds).

Pressing the RATE ke once enters SLOW update mode. This

increases the dela from 300msec to 3secs giving more time for

each digitising of the waveform to be observed carefull . Pres-

sing the ke again returns to normal update rate.

Holding the RATE ke depressed for two seconds enters FAST

update mode. This reduces the dela from 300msec to 20msec

giving a virtuall instant update which mimics a real-time

oscilloscope. Pressing the ke again returns to normal update

rate.

Entering FAST update mode reduces the acquisition memor

size to 1K words per channel and disables all of the trace

control functions except for trace position. Search mode

(COMP/ SCAN/MAG) and Average (AVG) are also disabled.

When RUN/HOLD is set to HOLD, the remaining 3K words per

channel of the digitising memor are set to zeroes and the

disabled functions are restored. Pre-trigger time dela is limited

to 10 divisions in FAST mode.

In "roll" and "repeat" modes the RATE ke is disabled.

R14. ROLL MODE OPERATION

In "roll" mode new data is written onto the right-hand side of the

displa as digitising takes place. Thus the waveform appears to

roll across the screen. The operation of the DSA524 in "roll"

mode (timebase speeds of 200msecs and below) is different from

its operation in other modes in several respects:

a) Triggering and Displa Update Rate

Because the waveform data is written continuousl onto the dis-

pla , it is not necessar to continuall stop and restart the digiti-

sing process. Consequentl when RUN /HOLD is set to RUN,

digitising takes place continuousl and triggering is disabled. The

RATE ke is disabled.

When RUN/HOLD is set to HOLD, triggering is enabled for

operation via the SINGLE ke . Pressing SINGLE commences the

"roll" and the trigger event stops it, thus the waveform data

captured is entirel pre-trigger data. Consequentl if a trigger

occurs immediatel , no data will be captured unless some post-

trigger time dela has been set. When the trigger mode is set to

AUTO, triggering occurs immediatel . When the trigger mode is

set to NORM, triggering occurs s nchronousl with the trigger

signal.

Because in "roll" mode the trigger stops the digitising process

instead of starting it, all the data in the digitising memor is pre-

trigger data unless some post-trigger time dela has been set.

Pre-trigger time dela is therefore not needed and is disabled.

b) Displa Window and Search mode

Because the waveform data is written continuousl to the screen

as digitising takes place, the displa shows the last part of the 4K

digitising memor instead of the first part. Because the left hand

edge of the displa window is set in steps of 100 words, onl 996

words are displa ed and the remaining 28 words are set to zero.

SEARCH can onl be selected in HOLD, and the scan window is

initiall set full to the right instead of full to the left.

c) Trace Controls

When in roll mode, operation of an of the trace controls (e.g.

gain variable) will effect onl the waveform data on the displa

which was captured after the control was changed. However,

when the digitising process is stopped, the new trace control

values will be applied to the whole of the contents of the

digitising memor including waveform data captured before the

change was made.

R15. REPEAT MODE OPERATION

In normal mode the DSA524 can digitise a waveform at up to

20MS /s digitising rate, equivalent to 5usecs per division. If the

waveform is repetitive (as opposed to being a single event) it can

digitise the waveform repetitivel , graduall building up the data

in the digitising memor . This mode of operation, known as

"repeat" mode, is used for timebase speeds of 2usecs and above

and provides equivalent digitising rates of up to 2GS /s (50nsecs

per div.). The operation of the DSA524 in repeat mode is

different from its operation in normal mode in several respects:

a) Triggering

Repeat mode requires a s nchronousl triggered waveform,

AUTO and LINE trigger modes are therefore disabled. Time dela

is not available (neither pre nor post trigger). The trigger event is

not captured, the first section of the waveform captured starts

350 nanoseconds after the trigger event.

b) Displa Update Rate

Repeat mode involves complex manipulation of data which can

take several seconds per digitisation. The displa update rate

varies between about one per second for a single channel at

2usecs/div to one ever 10 seconds for both channels at

50nsecs/div. The Rate ke is disabled in repeat mode.

R16. CURSOR MEASUREMENT

Moveable cursors allow accurate measurements of voltage and

time to be made on either Trace A or Trace B via an on-screen

digital readout.

To select cursor measurement, press the ke marked ON/OFF

within the numeric ke pad. Cursors will appear on Trace A, and

Trace B will be suppressed. Pressing the ke marked A/ B

selects Trace B instead of Trace A. To turn cursor measurement

off press the ON/OFF ke again.

Cursor measurement.

The cursors are flashing horizontal lines which each terminate

at a point on the waveform. The reference cursor is on the left

hand side of the screen, the delta cursor is on the right hand

side. The measurement is made between the two lines. The

readout shows the voltage and time difference between the end

of the reference cursor line and the start of the delta cursor

line. The cursors are moved using the arrow ke s marked REF

CURS and ∆ CURS respectivel .

R17. PROGRAM MODE

The DSA524 can operate as a full programmable instrument. It

can "learn" individual or sequential front panel settings, store

them in non-volatile memor , and "repla " them on demand.

Up to 50 settings can be stored.

Each front panel setting includes the state of ever ke and

rotar control and the source of each trace waveform. Thus if a

setting is "learned" which includes a trace recalled from a wave-

form store, that same store will be recalled again when the set-

ting is "re-pla ed". Thus reference waveforms can be recalled

automaticall within PROGRAM mode.

To "learn" one or more settings press the LEARN ke , this turns

on learn mode. The displa will show the message "NEXT

POSITION = NN" for 3 seconds where NN is a number between

01 and 50 corresponding to the position set when the unit was

last used.

To store a front panel setting in this position, ensure that the

front panel is set as required and press the SET/NEXT ke . The

displa will show the message "STORED IN NN" followed b

"NEXT POSITION = NN + 1". To store another front panel set-

ting, reset the front panel as required and press the SET/NEXT

ke again. To store the setting in an other memor position,

press the SET(NN) ke followed b a two digit number between

01 and 50.

The next memor position can be checked at an time b

pressing the LEARN ke again.

To "repla " one or more settings press the REPLAY ke , this

turns on repla mode. The displa will show "NEXT POSITION =

NN" as for learn mode. To repla the front panel setting cor-

responding to this position press the SET/NEXT ke . The displa

will show "REPLAYED FROM NN" followed b "NEXT POSITION

= NN + 1". Press the SET/NEXT ke again to repla this next

position. To repla an other position press the SETINN) ke

followed b a two digit number between 01 and 50.

The next memor position can be checked at an time b

pressing the REPLAY ke again.

Whenever the front panel is set using the repla mode all the

rotar controls become inoperative. To make an rotar control

operative again press the ke directl to its right. (Press once if

the lamp above the ke is on, or twice if it is off.)

To exit either learn or repla modes press the LEARN and

REPLAY ke s simultaneousl .

R18. SINE INTERPOLATION

When the displa mode is set to MAG (magnif ) the number of

true samples shown across the screen is reduced to 102. Al-

though 1,024 samples are displa ed, 9 samples out of each block

of 10 are mathematicall calculated using linear interpolation.

Linear interpolation provides a good reconstruction of the original

waveform provided that either the number of samples per c cle

of the waveform is reasonabl high (i.e. ten or more) or, if the

number of samples is low, that the original waveform is made up

mainl of linear elements (e.g. pulse, sawtooth, triangle

waveforms).

When the waveform is basicall sinusoidal and the number of

samples per c cle is low, linear interpolation will not provide a

satisfactor reconstruction and sine interpolation should be used

instead. Sine interpolation uses a mathematical curve fitting al-

gorithm and can provide a near perfect reconstruction of a sine

wave from onl four samples per c cle. See Appendix C for a

detailed discussion of interpolation.

Pressing the SINE INTERPOLATE ke toggles the function on or

off as indicated b the lamp above the ke . Interpolation is onl

active when the SEARCH mode is set to MAG. Sine interpolation

slows down the displa update rate considerabl .

R19. AVERAGE

The RUN AVERAGE function allows a number of digitisations of

the waveform to be summation averaged before being displa ed.

This improves the signal to noise ratio of a nois signal and can

often enable a signal to be observed that would otherwise have

been masked b large amounts of HF or LF noise. The average

function reduces the size of the digitising memories to 1K words

per channel.

The number of waveform digitisations which are averaged can be

Set to an number between 2 and 256. To change the number of

readings averaged press SHIFT (ke 8) followed b SET AVG (ke

4). The current averaging value is shown on the displa and can

be incremented or decremented using the REF CURS ke s (ke s 2

and 3). When the required number is displa ed, press ESCAPE.

Pressing the RUN AVERAGE ke enables averaging, pressing the

ke again disables it again, the status is indicated b the lamp

above the ke . Acquisitions continue to be controlled b the

RUN/HOLD and SINGLE ke s.

When the displa update rate is set to NORM the displa is

updated onl whenever the total number of averages has been

completed. When the update rate is set to SLOW the displa is

updated continuousl as averaging takes place. The displa

shows the number of averages currentl accumulated.

Note that averaging slows down the displa update rate. This is

particularl so at fast timebase speeds in "repeat" mode and slow

timebase speeds in normal mode.

R20. A= AXB (TRACE MULTIPLY)

This function provides a displa of the Trace A waveform multi-

plied b the Trace B waveform. It is particularl useful for ob-

taining power waveforms.

Press SHIFT (ke 8) followed b AxB (ke 2). The two waveforms

will be multiplied together and displa ed on Trace A (Trace B

continues to be displa ed). To return to a normal displa press

ESCAPE.

The multiplied waveform is scaled using units of one screen

division with the centre of the screen being zero. The traces are

multiplied exactl as the appear on the oscilloscope displa in-

cluding offsets introduced b the trace position controls. Thus at

a point where the position of Trace A is +2 divs and of Trace B is

—1.5 divs, the value of the multiplied waveform will be — 3 divs.

It should be noted that if either trace has values greater than ± 1

divs then overflows could occur on the multiplied waveform. The

displa ed waveform is limited to ± 4.25 divisions and conse-

quentl —3 divs multiplied b —2.5 divs will be displa ed as +

4.25 divs instead of + 7.5 divs.

The AxB function cannot operate while digitising is taking place.

Pressing the AxB ke will set RUN/HOLD to HOLD. The function

multiplies the traces exactl as the appear at the moment that

the AxB ke is pressed. When the function is enabled all of the

trace controls are inoperative with the exception of the Trace A

position control which can be used to adjust the position of the

multiplied waveform.

R21. LINE OR DOTS DISPLAY

In line displa mode the 1,024 individual points of the displa

are joined with angled lines to simulate one continuous line.

This gives a displa which is easier to view and less subject to

visual aliasing than one made up of dots (see Appendix B).

Sometimes, however, it is desirable to see the exact points on

the waveform where samples have been taken, along with their

levels. Pressing SHIFT (ke 8) followed b DOTS (ke 7) causes

the points to be joined b right-angled lines which form a stair-

case. Since the horizontal lines are brighter than the vertical

ones, this gives an impression of dots and makes it easier to

see each sample point and its associated level.

Also the line displa ma reduce the amplitude of waveforms

where successive samples can have ver large vertical

separations. Such a waveform will also appear brighter if a dots

displa is used.

To return to a line displa press LINE (ke 7). The unit defaults

to a line displa after RESET.

R22. PLOT

The waveforms shown on the oscilloscope displa can be sent

either to a digital X-Y plotter (HP-GL compatible) using the RS-

423 interface; or to an analog X-Y plotter or Y-T chart recorder

using the analog plotter interface.

The plot function can be directed either to the RS-423 interface

for use with a digital plotter, or to the analog plotter interface.

The DSA is factor initialised for use with a digital plotter. To

change to use with an analog plotter ke in "function 26" (press

FUNCTION NN, followed b 2 followed b 6). To return to use

with a digital plotter ke in "function 27".

a) Digital Plotter

The digital plotter must be compatible with HP-GL plotting com-

mands and must be fitted with a serial interface for connection

to the RS-423 interface socket of the DSA. For details of making

connections and of setting the baud rate see Section R25

’RS-423 Interface’. Alternativel , if the DSA has the IEEE-488

interface option fitted, a plotter with an IEEE-488 interface ma

be used.

To commence plotting press PLOT (ke 6), the time and voltage

per division and a graticule will be plotted followed b Trace A

followed b Trace B. If the plotter is a multi-pen plotter the text

and the graticule will be plotted using pen 1, Trace A will be

plotted using pen 2, and Trace B will be plotted using pen 3.

The entire plot fits onto an A4 sized sheet. To abandon plotting

at an stage press ESCAPE.

b) Analog Plotter

The analog plotter interface is mounted on the rear panel and

comprises five 4mm sockets marked X, YA, GND, YB, and PL

(pen lift).

The waveforms for Trace A and Trace B are sent simultaneousl

to their separate output sockets along with an X axis signal for

use with X-Y plotters. The 10.24 divisions of the displa are

plotted using a level of 100mV/div (for both Y and X) at a rate

selectable as 1, 2, 5 or 10 seconds per division. The pen-lift

signal is normall "low to lift" but can be inverted.

To set the plot rate, press SHIFT (ke 8) followed b SET PLOT

(ke 5)., The oscilloscope displa will show the present plot

rate. Press one of the REF CURS ke s (ke 2 or 3) to select a

new value, then press ESCAPE.

To commence plotting press PLOT (ke 6). The oscilloscope dis-

pla will show a series of prompts for setting the plotter. If RUN /

HOLD is at RUN it will be set to HOLD. To abandon plotting

before it is completed press ESCAPE.

A more complete description of the analog plotter PLOT function

is given in Appendix D.

R23. PRINT

The waveforms shown on the oscilloscope displa can be con-

verted to hard-cop using a dot-matrix printer. The printer must

be compatible with EPSON graphics commands (including quad

densit bit mapping) and must be fitted with a serial interface for

connection to the RS-423 interface socket of the DSA. For details

of making connections and of setting the baud rate see Section

R25. Baud rates below 2400 are not recommended as the

printing time becomes excessive.

The waveforms are printed with an 8x10 graticule using the same

1:1 aspect ratio as the oscilloscope displa . The are preceded b

several lines of text which detail the present settings of the DSA.

Line feeds are arranged so that two prints will fit onto one sheet

of 11 inch paper.

To commence printing, press SHIFT (ke 8) followed b PRINT

(ke 6). RUN /HOLD will be set to HOLD and printing will com-

mence. To abandon printing before it is completed press ESCAPE.

R24. REMOTE CONTROL AND DIGITAL DATA TRANSFER

The DSA can be full controlled via its RS-423 serial interface or

its IEEE-488 interface (if fitted). An thing that can be controlled

from the front panel can also be controlled via these digital inter-

faces. Waveform data can be sent to and from the DSA using the

interfaces, and a variet of other functions are also available.

The software commands for use on either of these interfaces are

listed in Appendix F. ‘Software Commands’.

R25. RS-423 INTERFACE

The DSA524 is fitted with an RS-423 serial interface which is full

compatible with equipment fitted with an RS-232C interface. It

can be used for remote control of the DSA, for bidirectional data

transfers and for connection to a printer or a digital plotter.

The RS-423 interface is connected via the 9 pin female D

connector mounted on the rear panel. The connections are as

follows:

Pin No. N me Function

2 RXD Input line for sending data to the DSA

3 TXD Output line for sending data from the DSA

5 GND Signal ground line

7 RTS Output line for handshaking (Request to

Send)

8 CTS Input line for handshaking (Clear to Send)

The interface operates with 8 data bits, 1 start bit, 1 or more

stop bits, no parit . If hardware handshaking is not being used,

pin 8 (CTS) must be pulled permanentl high, this can be done

b linking it to pin 7 (RTS) and forcing RTS permanentl high b

using function 83 (see Section R27). X-on/X-off handshaking can

be used as an alternative to hardware handshaking.

The baud rate is adjustable in binar steps between 300 baud

and 38,400 baud. Once set, the baud rate is stored in non-

volatile memor and will remain set. As shipped from the factor

it is set to 9,600 baud.

To change the baud rate press SHIFT (ke 8) followed b SET

BAUD (ke 3). The displa will show "baud rate = 9600" (for

example). Use the reference cursor ke s (ke s 2 and 3) to

increase or decrease the rate, then press ESCAPE. If the DSA is

not connected to an oscilloscope the baud rate ma be set

directl using the FUNCTION NN ke (see Section R27).

Note that as well as the options of 300 through to 38,400 there is

a further option of IEEE. This option is exclusivel for use when

the optional IEEE-488 interface board is installed and enabled.

Note that the RS-423 interface cannot be used when the IEEE-

488 interface is enabled.

Further details of making connections to the RS-423 interface

are given in Appendix E.

A description of the software commands for remote control and

data transfer via the interface is given in Appendix F.

R26. GP-IB (IEEE-488) INTERFACE

An optional module is available which interfaces the DSA524 to

the General Purpose Interface Bus (GP-IB) using the IEEE-488

standard. This option makes all of the functions which are avail-

able via the RS-423 interface also available via the GP-IB inter-

face. The interface can be used either with a controller or with-

out a controller in "talker onl " mode for connection to a printer

or digital plotter.

A full description of the fitting and operation of the GP-IB inter-

face module is provided in the separate manual supplied with it.

A description of the software commands for remote control and

data transfer via the interface is given in Appendix F. ‘Software

Commands’.

R27. DIRECTLY ACTING FUNCTIONS

Some of the parameters of the DSA which are normall set

interactivel using the text readout on the oscilloscope displa

can also be set directl using the FUNCTION NN ke . These

include setting the baud rate for the RS-423 interface and

setting the analog plotter rate.

A full list of these functions is given below:

Set Analog Plotter Rate 1sec /div 21

2sec/div 22

5sec/div 23

10sec/div 24

Select Analog Plotter Routine auto version 25

Select Analog Plotter Routine prompted version 26

Select Digital Plotter Routine 27

Set Baud Rate 300 30

600 31

1200 32

2400 33

4800 34

9600 35

19200 36

38400 37

IEEE-488 mode 38

Turn bandwidth limiting off 80

Turn bandwidth limiting on (factor default) 81

(a bandwidth limit of about 6MHz is applied

except in repeat mode)

Enable hardware handshaking via RTS (factor default) 82

Disable hardware handshaking via RTS 83

(disabling RTS handshaking forces RTS permanentl high)

Note that the RESET function cancels the effect of Function 80.

The following functions are intended for use b Service Engin-

eers onl (in conjunction with the appropriate service manuals):

Start analog plotter calibration routine 20

Check displa lamps 70

Check ke board switches 71

Check rotar controls 72

Check DAC output waveform 73

Check RS-423 operation 74

Check Autocal values 75

Return b tes from RS-423 input buffer 76

Clear all set-up parameters 78

Function 78 can be used if the DSA appears to have suffered a

program corruption from which it cannot be made to recover

either b switching the DSA off or b using the RESET function.

Note that the contents of all the memories including the

indexed waveform stores and the PROGRAM memor will be

cleared. Function 78 restores the DSA to the same state as

when it left the factor .

USERS TUTORIAL

The sophisticated facilities of the DSA524 have resulted in a fairl complex instrument. This "hands-on" tutorial takes the user through

most of the functions of the unit step b step, and provides an eas method of gaining familiarit with its operation.

New users should follow the tutorial exactl and resist the temptation to experiment with functions before the have been covered.

Existing users ma find the tutorial useful for covering functions with which the are not et familiar. Each section is complete in itself

and commences with the DSA being "reset" using SHIFT followed b RESET, and with the signal generator being set to SINE, 20kHz,

5V pk-pk.

INDEX TO THE TUTORIAL

P ge

Equipment Required 10

Setting up the Equipment 10

First Steps 10

What to Expect 10

The Displa Oscilloscope 10

Front Panel Controls 10

Getting out of Trouble 10

P rt One The Basic Functions.

Controlling Digitising 10

Controlling the Input Channels 11

Controlling the Traces 11

Setting the Timebase 12

Normal Mode 11

Roll Mode 12

Repeat Mode 12

Triggering 12

P rt Two More Advanced Functions.

More about Triggering 12

More about Roll Mode 13

Memor Search 13

Displa Update Rate 13

Indexed Waveform Memories 14

Cursor Measurement 14

Averaging 14

Dot Joining and Interpolation 14

Trace Multipl 15

Program Mode 15

Hardcop Output 15

Remote Interfacing 15

A Final Word 15

Equipment Required

1. A conventional real-time oscilloscope for the displa , the

minimum specification: 5MHz bandwidth, single channel,

8x10 division graticule.

2. A wide frequenc -range signal source, preferabl a

function generator. (The tutorial assumes that a function

generator is being used.)

3. Three BNC to BNC connecting cables.

Setting-up the Equipment

1. Connect the rear panel BNC socket of the DSA marked

"composite" to the CH1 input of the oscilloscope.

2. Set the oscilloscope as follows:

Mode: Single channel (CH1)

CH1 input coupling: DC

Sensitivity: 100mV/div

Timeb se: 50usecs/div

Trigger source: CH1 (not vertical mode)

Trigger coupling: AC

Trigger slope: Negative

Trigger Level: Negative (slightl )

Sweep del y, sweep

hold-off etc: Zero or minimum

3. Connect the main output of the function generator to the

CH1 input of the DSA. Connect the S nc or TTL output to

CH2.

First Steps

1 Switch on the DSA (the power switch is at the rear). The

oscilloscope should then show the message "CENTRE

ARROW TIP" (alternating with "THEN PRESS ESCAPE").

Adjust the trigger level if necessar .

2. Adjust the vertical and horizontal shift controls of the os-

cilloscope until the arrow tip is in the centre of the

graticule.

3. Set the function generator to SINE, 20kHz, 5V pk-pk.

4. Press the ESCAPE ke . Then press SHIFT followed b

RESET. This ensures that all of the more complex func-

tions are cancelled, and that the DSA is put into a known

state as follows:

Both channels ON, 1V /div, AC coupled, 20usec/div AUTO

trigger from CH 1.

The displa should now be showing a sine waveform and

a pulse waveform, each of around 5 divisions pk-pk ampli-

tude and around 2.5 divisions period.

Wh t to Expect

The unit is now operating as a digital storage oscilloscope. Both

input signals are being repetitivel digitised b an analog to

digital converter (ADC), and stored in a memor the contents of

which is being converted back into analog signals b a digital to

analog converter (DAC) and then displa ed on the screen via a

displa multiplexer. This process takes a little time, introducing a

slight dela between a change occurring at the input and that

change appearing on the displa .

The displa multiplexer mixes together the two traces, the trigger

signal and, when needed, text. At the far left of the screen the

valid section of the trace is preceded b a ver narrow negative

pulse followed b a horizontal line at the trace zero level (this can

be removed b using a two cable connection — see Appendix A).

Following the valid section, at the far right of the screen, the

trace is shifted up to the top of the displa area.

When the displa is correctl centred, the valid section of the

traces starts 0.12 divisions to the left of the graticule and ends

0.12 divisions to the right of it. If the timebase of the displa

oscilloscope is not perfectl calibrated, the valid section ma be

slightl longer or shorter than this.

Each trace is made up of 1024 samples across 10.24 horizontal

divisions of the screen (100 samples per division). Each sample

can be at an of 256 levels within 8.53 vertical divisions (30

levels per division).

Because the displa is made up of discrete steps, waveforms do

not look quite the same as the do with an analog oscilloscope.

The minimum level change between samples is one thirtieth of

a division, and even where the input signal level is constant the

digitised level ma var slightl . This variation is caused b

noise on the signal, noise in the input amplifiers, or digitising

noise in the ADC (t picall ± )bit) and results in the digitised

waveform looking slightl "ragged" when compared with an

analog oscilloscope. Noise on the waveform of an analog

oscilloscope is averaged out b the e e.

The Displ y Oscilloscope

Once the displa oscilloscope has been set up, no further use

need be made of its controls except for occasional re-centering

of the trace to correct for an warm-up drift. To re-centre the

trace press the two ke s marked "SET 'SCOPE" (on the lower

right of the DSA) and adjust the oscilloscope's position controls

to centre the arrow tip.

Front P nel Controls

The front panel of the DSA524 is completel "cold", that is to

sa that there are no direct links between the front panel and

the circuitr . All of the controls, including the rotar ones, are

monitored b a microprocessor which then performs the con-

trol. All of the switches are of a momentar non-latching t pe

whose status is indicated either b lamps under the panel or,

where appropriate, b text on the displa . This s stem enables

complete digital programming of the front panel when required.

The ke s within the numeric ke pad section (right-hand side of

unit) have up to three functions. Their normal function is

printed in black above each ke . After the SHIFT ke is pressed

the function becomes as printed in green above the ke . When

a function ending in (NN) is pressed (e.g. SAVE(NN)) the ke

will enter the number printed alongside it.

Note that when SHIFT or a function ending in (NN) is pressed,

the lamp marked ENTER will flash to indicate that one or more

further ke presses is required. An function that causes the

ENTER lamp to flash can be cancelled b pressing that function

ke again.

Note that some of the functions (including SET 'SCOPE) auto-

maticall set the RUN/HOLD function to HOLD. If digitising

ceases unexpectedl check the condition of RUN /HOLD.

All of the front panel settings are retained when the power is

turned off (except for RUN /HOLD which is alwa s set to HOLD

at power-on).

Getting out of Trouble

If at an stage ou lose track of the operation of the DSA, it can

be reset to a known state b pressing SHIFT followed b RESET

(as in First Steps). Each section of the tutorial starts with the

DSA in the "reset" state and the generator set to SINE, 20kHz,

5V pk-pk. Thus it is eas to restart the tutorial at the beginning

of an section.

PART ONE — BASIC FUNCTIONS

The functions covered in this first part of the tutorial are the

ones necessar to operate the DSA524 as a basic digital storage

adaptor.

Controlling Digitising

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The digitising of the input signals is controlled b the two ke s

at the top of the TRIG section marked RUN /HOLD and SINGLE.

1. When RUN/HOLD is set to RUN, digitising is repeated

continuousl . Tr changing the amplitude or frequenc

of the generator and note how the displa is updated

about three times each second.

2. When RUN /HOLD is set to HOLD, digitising is stopped.

Press RUN /HOLD to set it to HOLD, then change the out-

put of the generator, and note how the displa remains

unchanged.

3. When RUN /HOLD is set to HOLD, pressing the SINGLE

ke causes digitising to occur once. Press SINGLE and

note how the displa is updated to the new amplitude/fre-

quenc of the generator.

Controlling the Input Ch nnels

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The two input channels CH1 and CH2 are identical. The control

the levels of the input signals before the are digitised.

1. The input coupling switches (AC/DC and GND) perform

the same function as on a normal oscilloscope. Tr

changing them. Note that when CH1 is grounded the

position of the CH2 waveform on the displa becomes

random, this is because the trigger signal has been

removed. Set both channels back to AC.

2. The input sensitivit is variable between 10V/div and 2mV

/div. The ke with a downwards arrow sets a lower

volts/div setting and the ke with the upwards arrow a

higher one, the ke s autorepeat if held depressed. Tr

changing the CH1 sensitivit upwards and downwards.

Note that when the input exceeds approximatel ± 4.25

divisions on the screen it becomes "clipped", this is

because the range of the digitiser is limited to ± 4.25

divisions. When the input signal is outside the range of the

digitiser, the AUTO/OVLD lamp flashes, this is to warn the

user that the signal is not being correctl digitised (no

damage is being done).

3. Autoranging input sensitivit can be selected on either

channel. Press both arrow ke s simultaneousl , the AUTO

lamp will come on. Tr changing the amplitude of the gen-

erator output and note how the sensitivit is automaticall

changed to maintain a screen amplitude of between about

1.5 and 3.5 divisions. To cancel autoranging press either

arrow ke once.

4. If the DC level of the input signal is not zero, it ma be

necessar to appl a DC offset to the signal before it is

digitised. This can be done with the rotar controls

marked OFFSET which can add up to ±8 divisions of

offset. Press the ke marked ZERO(VAR) to enable

variable offset (it is enabled when the lamp is off). Tr

rotating the offset control and note how the DC level of

the signal is changed. Press the ke again to return to

zero offset.

5. The digitising for each channel can be controlled

individuall b the ke s marked "ON/OFF". These allow

one channel to be "held" while digitising continues on the

other channel. Tr turning CH1 off and changing the fre-

quenc of the generator, note that the CH2 displa con-

tinues to be updated but that the CH1 displa is frozen.

Note that if both channels are turned off, RUN/HOLD will

be automaticall set to HOLD.

Controlling the Tr ces

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 can displa two traces simultaneousl , the traces are

called Trace A and Trace B. Whereas the input channel controls

(CH1 and CH2) operate on the input to the digitiser, the trace

controls operate on the output signals which are sent to the

displa oscilloscope. Normall Trace A is used to displa CH1, and

Trace B is used to displa CH2, but the traces ma alternativel

be used to displa waveforms stored in the indexed memories.

1. The POSITION controls define the position of the traces

on the screen and provide ± 4.25 divisions of adjustment.

Press the ke marked HOME(VAR) to enable variable posi-

tion (it is enabled when the lamp is off). Tr var ing the

position of the traces, note that whereas OFFSET onl

affects the waveform when digitising is taking place, PO-

SITION affects it at all times whether RUN/HOLD is at

RUN or HOLD. Press the ke again to "home" the trace

position.

2. The GAIN VARIABLE controls can reduce the amplitude

of each trace b an factor between one (full clockwise)

and five (full anti-clockwise). Press the CAL(UNCAL) ke

to enable variable gain (it is enabled when the lamp is

off). Tr var ing the gain and note that, because it is

within the trace control section, it operates on the

waveform after it has been digitised and continues to

operate even when the waveform is "held". Press the

ke again to return to calibrated gain.

3. Each trace is turned off b simultaneousl pressing the

ke s marked CH1 (or CH2) and RCL(NN). Tr turning a

trace off (note that the CH ke should be pressed first to

avoid setting RUN/HOLD to HOLD). To turn the trace

back on press the CH1 (or CH2) ke . Do not tr using

the RCL(NN) or SAVE(NN) ke s at this stage.

4. Trace B has a ke marked INV (Invert). Press this ke

and note that the trace becomes inverted. Press it again

to turn inversion off.

5. Trace A has a ke marked ADD B. Press this ke and

note that Trace A then displa s the sum of the Trace A

waveform and the Trace B waveform. Note that this can

also be used for subtraction when Trace B is set to

invert. Note also that because add and invert are trace

controls the can still be used when either or both

channels are "held".

Setting the Timeb se

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The timebase is adjustable between 50ns/div and 200mins/div.

The timebase speed is set using the two TIME/DIV ke s which

autorepeat if held depressed. Setting the timebase speed also

sets the DSA into one of three modes of operation:

1. Normal Mode

1a. Turn off CH2 and Trace B. Tr changing the generator

frequenc up and down and changing the timebase

speed to maintain a roughl constant period on the

screen (within the range 5us/div to 100ms/div). This is

the "normal" mode of operation whereb the displa is

updated each time 40.96 divisions of the waveform have

been digitised. Note that at low timebase speeds the

displa update rate becomes slower, this is because of

the increased digitising time (at 100ms/div digitising

takes 4.096 seconds).

1b. Now set a generator frequenc of 100Hz and a timebase

speed of 5ms/div. Increase the generator frequenc to

1kHz, note that the waveform is starting to become diffi-

cult to view. Increase to 2kHz, note that the waveform

can no longer be interpreted as a sine waveform and

appears to have random patterns superimposed onto it.

This is visual aliasing (caused b the vertical separation

between sample points being much greater than the

horizontal separation). Turn on the sweep magnifier of

the displa oscilloscope to observe that the waveform is

roughl sinusoidal but is made up of onl 10 samples per

c cle.

1c. Now increase the generator frequenc to 20kHz and var

it slightl , note that the waveform changes erraticall as

the generator frequenc is changed, and that waveforms

with an apparent frequenc down to a few Hz can be

obtained. This is true aliasing, caused b the sampling

frequenc being less than twice the signal frequenc

(the sampling rate equals 100 divided b the time/div,

so at 5ms/div the sampling rate is 20kS /s).

Aliasing effects are common to all digital storage instru-

ments. Note that to avoid true aliasing the sampling rate

must be greater than twice the signal frequenc (time/div

= 50/f) and to avoid visual aliasing the rate must be

greater than ten times the signal frequenc (time/div =

10/f).

1d. The DSA524 incorporates a feature which automaticall

sets the timebase to avoid aliasing effects and to provide

a sensible waveform period on the screen. Turn off the

sweep magnifier on the displa oscilloscope. Press simul-

taneousl the two ke s marked AUTOSET within the

timebase section, note that the timebase is automaticall

set to 20us/div.

1e. Tr changing the generator frequenc and using

AUTOSET, note how it sets the timebase to maintain

between 4 and 10 c cles of the waveform across the

screen. (AUTOSET can onl operate when a trigger signal

of 50Hz or above is being generated.)

2. Roll Mode

For timebase speeds of 200ms/div and slower, the DSA

enters roll mode (indicated b an audible "beep" and

illumination of the ROLL lamp). In roll mode the waveform

data is written onto the screen continuousl as it is being

digitised. This avoids the long dela s that would occur if

the screen was onl updated after digitising was

completed.

Set the timebase to 200ms/div and the generator to 2Hz,

note how the waveform appears to "roll" across the

screen. Tr setting slower timebase speeds and lower

generator frequencies (DC coupling will be necessar for

lower frequencies). Set the timebase as slow as it will go,

note that below 500s/div the SEC and mSEC lamps illumi-

nate together to indicate minutes (speeds as low as 200

minutes/div can be set enabling waveform capture over

man hours).

3. Repeat Mode

The maximum sampling rate of the DSA524 is 20MS /s

(which is obtained at 5us/div). This is the maximum rate

that can be used to capture single event signals. However,

if the signal is repetitive, repeat mode can be used. This

builds the waveform up b repeatedl digitising it, and can

provide equivalent sampling rates up to 2GS /s. For time-

base speeds of 2us/div and faster the DSA enters repeat

mode (indicated b a "beep" and illumination of the RPT

lamp).

3a. Set the generator to 200kHz and set the timebase set to

2us/div (or press AUTOSET), note that the waveform is

being digitised at an equivalent rate of 50MS /s. Var the

generator frequenc slightl and note that the displa

update rate is slower in repeat mode, and that the first

screen update after the signal is changed is invalid (this is

because the waveform is built up from multiple

digitisations).

3b. Ground the CH1 input and note that updating of the

screen ceases and a message "NO TRIGGER" appears on

the screen (this is because repeat mode requires a repeti-

tive trigger signal to be able to operate). Un-ground the

input and increase the generator frequenc . Increase the

timebase speed and note that waveforms up to 35MHz

can be captured (this is limited b the input amplifier

bandwidth of the DSA) using timebase speeds of up to

50ns/div (2GS /s equivalent sampling rate). Note also that

the update rate is slowest at the fastest timebase speeds

when in repeat mode.

4. Turn on CH2 and Trace B. Note that the repeat mode

update rate is slower when both channels are turned on.

Set the timebase speed down to 20us/div noting that

when both channels are on, the ALT lamp illuminates for

speeds of 10us/div and faster, and that the CHOP lamp

illuminates for speeds of 20us/div and slower. CHOP

indicates that both input channels are digitised together

(on opposite c cles of the sampling clock) while ALT

indicates that the input channels are digitised alternatel

(CH2 followed b CH1). Thus if digitising is un-triggered,

or if the input signals do not have a constant relationship

to the trigger signal, phase relationships between the

signals will not be maintained above 20us/div.

Triggering

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The trigger controls for the DSA524 are broadl similar to those

on a conventional oscilloscope. The exceptions are EVENTS DLY

and TIME DLY.

1. SOURCE The source of the trigger signal can be CH1,

CH2, or EXT (external via the BNC socket below the

trigger controls). Note that onl AC coupling is available

via the external input.

2. MODE The mode switch has three positions, AUTO,

NORM, and LINE. AUTO mode is similar to Bright-Line

Auto on a conventional oscilloscope. Digitising is perfor-

med in s nchronism with the trigger signal but, if the

trigger signal ceases or the trigger repetition rate falls

below 20Hz, digitising continues but without s nchro-

nism. In NORM (normal) mode, digitising stops if the

trigger signal ceases. In LINE mode, digitising is

performed in s nchronism with AC line (50 or 60 Hz).

Tr removing the trigger signal b setting SOURCE to

external, note that digitising continues (without

s nchronism) in AUTO mode, but ceases in NORM mode.

LEVEL, SLOPE and COUPL (coupling) The function of

these controls should be self explanator . To enable

variable trigger level, press the ke marked ZERO(VAR

I (variable level is enabled when the lamp is off). Tr

using all of the trigger controls, then return them to

their original settings.

PART TWO — MORE ADVANCED FUNCTIONS

The functions covered in the first part of the tutorial enable the

user to operate the DSA524 as a basic digital storage

oscilloscope. This second part covers the more advanced

features which would not be found on a basic DSO.

More bout Triggering

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

1. TIME DLY (time dela ) With TIME DLY off, digitising

starts immediatel following a trigger. Thus the left-hand

edge of the trace shows the waveform immediatel after

the trigger point. TIME DLY shifts the point at which

digitising starts to allow the trace to show the waveform

either before the trigger (pre trigger dela ) or after the

trigger (post trigger dela ).

Set the generator to 5kHz; the trace should now show

about one c cle of the waveform starting at the trigger

point. Press the TIME DLY (minus) ke , note that the

message "TIME DLY = +0000 DIV" is displa ed. Press

the ke again to decrement the number to —0001 (note

that the ke s onl increment or decrement when the

message is being displa ed, on the first press the

merel cause the current dela value to be shown).

The trace should now start one division before the

trigger point. Tr incrementing and decrementing the

dela using the + and — ke s, note that the trace can

be positioned an where relative to the trigger point (in

steps of one division) and that the PRE and POST lamps

illuminate for negative and positive dela s respectivel .

The maximum pre trigger dela is —40 divs and the

maximum post trigger dela is + 9999 divs. Note that

the + and — ke s autorepeat if held depressed, and that

the dela can be set back to zero at an time b

pressing both ke s simultaneousl .

Post trigger time dela can be used to expand a small sec-

tion of a waveform (as in a sweep-dela oscilloscope). Set

a dela of +0002 so that the peak of the sinewave is

within the first division of the screen. Now increase the

timebase to 5usec/div, note that the dela is increased to

+0008 divs so as to maintain a constant time dela thus

keeping the sinewave peak within the trace area.

Note that time dela is not available in RPT mode, and

that onl post trigger time dela is available in ROLL

mode. Time dela is automaticall set to zero whenever

the timebase is set into RPT or ROLL.

2. EVENTS DLY (events dela ) This function enables the

triggering of the digitising to be dela ed b up to 15

trigger events. See the reference section of the manual for

a full explanation.

More bout Roll Mode

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

Because in roll mode the waveform data is written continuousl

onto the displa , it is not necessar to continuall stop and

restart the digitising process. Consequentl when RUN/HOLD is

set to RUN, digitising takes place continuousl and triggering is

disabled.

The purpose of triggering is to enable a specific part of a wave-

form to be captured. In normal modes the digitising period is

alwa s 40 divisions, so defining the trigger point automaticall

defines the part of the waveform that will be captured. In roll

mode the digitising period is not limited to 40 divisions but con-

tinues indefinitel .

There are two possible wa s in which a triggered roll mode can

be provided. The trigger could start the roll which could then

continue for 40 divisions, but this would have the disadvantage

that pre-trigger data could not be captured. Alternativel , the roll

could run continuousl until stopped b the trigger, this is the

s stem emplo ed in the DSA524 when SINGLE is used.

1. Set the generator frequenc to 2Hz and the DSA timebase

to 200ms/div. Select DC input coupling.

2. Set RUN /HOLD to HOLD, ensure that the trigger mode is

AUTO and that TIME DLY is off. Now press SINGLE, note

that although the roll starts, it stops again immediatel .

This is because in AUTO mode triggering occurs auto-

maticall after a ver short dela .

3. Now set TIME DLY to +0005 divisions. Press SINGLE and

note that the roll stops after 5 divisions of data has been

captured.

4. Set TIME DLY back to zero and set the trigger mode to

NORM. Press SINGLE and note that a small section of the

waveform prior to the trigger level point has been cap-

tured. Thus the waveform occurring between SINGLE

being pressed and the trigger occurring has been

captured.

Note that in roll mode SINGLE, all the data in the digitising

memor is pre-trigger data unless some post-trigger time dela

has been set. Pre-trigger time dela is therefore not needed and

is disabled.

Similarl , when in roll mode the displa alwa s shows the last

section of the digitising memor rather than the first. Therefore

when SEARCH mode is selected, the SCAN window is initiall set

full right instead of full left.

Memory Se rch

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

Although the screen shows onl 1024 words (10.24

divisions) for each trace, the digitising memor captures

4096 words (40.96 divisions) per channel. The SEARCH

ke enables the whole of the digitising memor to be

accessed. It also provides digital magnification b ten

(using linear interpolation).

1. Press SEARCH once, the COMP (compress) lamp will illu-

minate and a filled bar will appear at the top of the

screen for 3 seconds (the filled bar represents the 4K of

the memor ). Note that the waveform is compressed b

a factor of four, thus allowing the whole of the digitising

memor to be displa ed (this is achieved b displa ing

ever fourth word).

2. Press SEARCH again, the SCAN lamp will illuminate and

a bar will appear at the top of the screen with the first

quarter filled (this bar represents the 4K of the memor

and the filled section represents the 1K which is being

displa ed). Note that the waveform returns to normal

and that the bar disappears after 3 seconds.

Press the ke marked SCAN /MAG which has a right-

hand arrow, note that the bar reappears. Press the ke

again, note that the waveform appears to r 'love to the

left b one division and that the filled section of the bar

moves to the right. The filled section can be regarded as

the "scan window" which shows which 1K section of the

4K memor is being displa ed.

Tr moving the scan window backwards and forwards

using the two arrow ke s. Note that the ke s onl move

the window whilst the bar is being displa ed, otherwise

the first press merel brings up the bar in order to show

the present position.

3. Press SEARCH again, the MAG light will illuminate and a

bar will appear with the first one tenth filled (the bar

represents the present position of the scan window and

the filled section represents the 102 words which are

being magnified to fill the screen, this can be regarded

as the magnif window). Note that the waveform

becomes magnified b x10 and that the bar disappears

after 3 seconds.

Tr moving the magnif window backwards and

forwards using the two arrow ke s. Note that this works

in just the same wa as with the scan window.

4. Press SEARCH several times and note how it c cles

through the COMP, SCAN and MAG functions. Press the

two SCAN /MAG ke s simultaneousl in order to turn

search off.

Displ y Upd te R te

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The rate at which digitising is repeated and the displa is

updated can be varied using the ke marked RATE. When the

rate is set to normal (SLOW and FAST lamps both off) there is a

dela of about 0.3 seconds before digitising is restarted when in

RUN mode. This dela can be increased to about 3 seconds or

reduced to about 0.03 seconds.

The RATE ke onl operates with timebase speeds between

100ms/div and 5us/div, it has no effect in ROLL or RPT modes.

1. Press the RATE ke (the SLOW lamp will illuminate) and

var the generator output. Note that the screen is

updated onl about once ever 3 seconds instead of

about 3 times per second. This gives enough time for

each digitising to be observed and for the displa to be

"held" before the waveform is lost and replaced with a

new one. Press RATE again to return to normal update

rate.

2. Press the RATE ke and hold it depressed for 2 seconds

(the FAST lamp will be illuminated) and var the

generator output. Note that the screen is updated ver

quickl providing a near instant response to waveform

changes similar to a conventional oscilloscope. Press

RATE again to return to normal update rate.

Selecting FAST update cancels an waveform processing

functions that have been selected including GAIN

VARIABLE, ADD B, INV, RUN AVERAGE and SEARCH.

Indexed W veform Memories

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 has 16 non-volatile indexed waveform memories.

These memories are each 1K words in size and are used to save

and recall waveforms from Trace A or Trace B.

1. Press the SAVE(NN) ke on Trace A, note that the ENTER

lamp flashes within the numeric ke pad section. Press ke

0 followed b ke 1, this stores the waveform currentl

displa ed on Trace A into memor 01. Note that the

screen shows "MEMORY 01 = TRACE A" and that RUN

/HOLD is set automaticall to HOLD.

2. Now press RCL(NN) on Trace B, followed b ke 0,

followed b ke 1, this recalls the waveform onto Trace B.

Note that the screen shows "TRACE B = MEMORY 01" and

that the MEM lamp (in the Trace B area) illuminates in

place of the CH2 lamp.

3. Set RUN /HOLD back to RUN, and change the generator

frequenc . Note that Trace B is now displa ing a reference

waveform which can be used for on-screen comparison

with the CH1 signal. Operate the Trace B invert and gain

variable functions, note that these operate on a recalled

waveform just as the do on a waveform sourced from an

input channel.

4. Press the Trace B RCL(NN) ke twice and note that

"TRACE B = MEMORY 01" is displa ed again, allowing the

user to check which memor is being displa ed at an

time. Press the CH2 ke on Trace B to return to a displa

of CH2.

The 16 memories are numbered 01 through to 16. The can onl

be used to store the contents of a trace memor (i.e. a waveform

displa ed on the screen). Recalled waveforms are not affected b

the SEARCH function.

Cursor Me surement

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 incorporates cursor measurement with on-screen

digital readout of voltage and time difference. Cursor measure-

ment can onl be performed in HOLD, and on onl one channel

at a time. The cursor line starts at the left hand edge of the

screen and intersects with the waveform at the reference cursor

point. It is then shifted upwards awa from the trace, continues

sidewa s and then comes down to intersect with the waveform

again at the delta cursor point before continuing to the right

hand edge of the screen. The measurement is made between the

two cursor points.

1. Press CURS ON/OFF (ke 4), Trace B will turn off and a

flashing cursor line will be displa ed. Note that RUN/

HOLD is set to HOLD and that the screen shows the

message "Delta A = XX.XV XXX.XuS" representing the

voltage difference and time difference between the two

points.

2. Tr moving each of the cursors using the arrow ke s

marked REF CURS and A CURS. Note that the cursor

points "track" the waveform automaticall and that the

cursor movement speeds up when the ke s are held de-

pressed.

3. Press CURS A/ B (ke 5), Trace A will be replaced with

Trace B. Note that the cursor points adjust automaticall

to the new waveform. Press CURS ON/OFF again to turn

cursor measurement off.

Averaging

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 can average an number of readings from 2 up to

255, enabling large improvements to be made to the signal to

noise ratio of nois signals. The average number is initiall set

to 16.

1. Turn off Trace B and note the waveform amplitude on

Trace A. Then remove the trigger signal b setting the

source to EXT. The waveform should now be

uns nchronized, this simulates random noise because

the phase of the signal is now random.

2. Press the RUN AVERAGE ke (within the timebase sec-

tion), the indicator lamp will illuminate to show that

averaging has been selected. The screen will show the

message "AVERAGE COUNT = X" where X increments

continuousl between 001 and 016. Note that the trace

is updated each time the message reaches 016 and that

the signal amplitude has been reduced, t picall b a

factor of four (trul random noise is attenuated b the

square root of the number averaged). Set the DSA to

HOLD and press SINGLE, note that averaging is

performed once onl .

3. Now press SHIFT (ke 8) followed b SET AVG (ke 4),

the message "AVERAGES = 016" will be displa ed

showing the current setting. Now tr using the REF

CURS arrow ke s to increment or decrement the

number. Set it to 064 and press ESCAPE to terminate

set-average mode. Re-start averaging, note that the

signal amplitude is now reduced t picall b a factor of

eight instead of four. Use SET AVG again to set the

averages back to 16.

The above mode of operation is known as a totalising

average because the screen is onl updated when the

total number of digitisings have been averaged. An

alternative mode is a running average whereb the

screen is updated each time digitising takes place.

4. Return the trigger source to CH1. Press RATE, the SLOW

lamp will illuminate. When SLOW and RUN AVERAGE are

both illuminated the mode is set to running average.

Press SINGLE, note that the screen is updated with the

new average value on ever count. Note that averaging

can be stopped at an time b pressing RUN/HOLD.

Averaging is not available in ROLL mode and onl a

totalising average is available in RPT mode. In RPT

mode the average number is onl displa ed each time

averaging is completed.

Dot Joining nd Interpol tion

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 is initialised to use analog dot joining. This links

the 1024 individual sample points on the screen with angled

lines to simulate one continuous line. This gives a displa which

is eas to view, and reduces the number of samples per c cle

required to avoid visual aliasing.

However, when the vertical separation between adjacent

sample points is large, dot joining can reduce the peak

amplitude of the waveform. To avoid this a "dots" displa can

be selected instead of a "line" displa . A dots displa also has

the advantage that the exact position and level of each sample

point can be viewed.

1. Set the generator to SINE, 20kHz (with the DSA at

20us/div) and turn on sweep magnif on the displa

oscilloscope. Press SHIFT followed b DOTS (ke 7),

note that the individual sample points are now visible.

2. Turn off the sweep magnifier and note that the displa

shows some visual aliasing. Return to a "line" displa b

pressing LINE (ke 7), note that the visual aliasing is

reduced.

The sweep magnifier of the displa oscilloscope provides an

analog expansion of the trace. The magnif function on the DSA

(via the SEARCH ke ) provides a digital expansion. 102 words of

the digitising memor are used to fill the 1024 words of the trace

b using linear interpolation to generate nine extra words

between each pair.

When a waveform has been captured at a ver low number of

samples per c cle, MAG can be used to observe it. If the

waveform is sinusoidal in nature, linear interpolation will not re-

produce the waveform shape ver well if the number of samples

per c cle is less than ten. The DSA524 provides the alternative of

sine interpolation which provides a good reconstruction of a

sinewave from onl four samples per c cle b using a mathe-

matical curve fitting algorithm.

3. Reduce the timebase speed to 100us/div, this reduces the

number of samples per c cle to five. Press SEARCH three

times to select MAG mode, note that the displa ed wave-

form shape is poor. Press the SINE INTERP ke , the lamp

will illuminate, note that the displa ed waveform shape is

greatl improved.

Tr ce Multiply

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The trace multipl function (A = AxB) allows the product of two

waveforms to be displa ed. Thus, for example, if Trace A was

displa ing a voltage waveform and Trace B was displa ing a

corresponding current waveform, trace multipl could be used to

displa the power waveform on Trace A.

1. Note the waveforms obtained on each trace then press

SHIFT followed b A = AxB (ke 2), RUN/HOLD will be set

to HOLD, note that the multiplied waveform appears on

Trace A.

2. Note that trace multipl cannot be used while digitising is

taking place (pressing RUN or SINGLE will cancel the

function). Note also that ADD B and GAIN VARIABLE on

Trace A are disabled after trace multipl has been

selected. Press ESCAPE to return Trace A to its normal

displa .

The multiplied waveform is scaled using units of one screen

division with the centre of the screen being zero. The traces are

multiplied exactl as the appeared on the oscilloscope displa

including offsets introduced b the trace position controls. Thus

at a point where the position of Trace A is +2 divs and of Trace B

is -1.5 divs, the value of the multiplied waveform will be -3 divs.

It should be noted that if either trace has values greater than ±1

divs then overflows could occur on the multiplied waveform. The

displa ed waveform is limited to ±4.25 divisions and

consequentl -3 divs multiplied b -2.5 divs will be displa ed as

+4.25 divs instead of +7.5 divs.

4. Use the Trace A and Trace B variable controls to alter

the amplitude and position of the waveforms prior to

multiplication. Note the results. Press ESCAPE to exit.

Progr m Mode

(Start with the DSA reset and the generator set to SINE, 20kHz,

5V pk-pk.)

The DSA524 can operate as a full programmable instrument. It

can "learn" individual or sequential front panel settings, store

them in non-volatile memor , and "repla " them on demand. Up

to 50 settings can be stored.

Each front panel setting includes the state of ever ke and

rotar control and the source of each trace waveform. Thus if a

setting is "learned" which includes a trace recalled from a wave-

form store, that same store will be recalled again when the

setting is "re-pla ed". Thus reference waveforms can be recalled

automaticall within PROGRAM mode.

1 Select "learn" mode b pressing LEARN (the LEARN lamp

will illuminate). Note that the screen shows the message

"NEXT POSITION = 01".

2. Press SET(NN), followed b ke 3, followed b ke 0 (for

'example). The screen will show the message "STORED

IN MEM = 30" followed b "NEXT POSITION = 31",

showing that the current front panel settings have been

stored in memor position 30.

3. Now reset the front panel including time/div, volts/div,

input coupling, rotar controls etc. Press SET/NEXT, the

screen will show "STORED IN MEM = 31" followed b

"NEXT POSITION = 32". Now recall waveform memor

01 onto Trace B and then press SET/NEXT again.

Further sets of front panel settings have now been

stored in positions 31 and 32.

4. Exit "learn" mode b pressing the LEARN and REPLAY

ke s simultaneousl , and select "repla " mode b

pressing REPLAY (the R PLY lamp will illuminate). The

screen will show "NEXT POSITION = 33", showing that

the most recentl used position was 32.

5. Press SET(NN) 30, the front panel will reset and the

screen will show "REPLAYED MEM = 30" followed b

"NEXT POSITION = 31". Press SET/NEXT, the front

panel will be reset again. Press SET/NEXT again, the

front panel will be reset and the waveform in memor 01

will appear on Trace B.

6. Press SET(NN) 30 to reset the front panel to its original

settings and exit "repla " mode b pressing the LEARN

and REPLAY ke s simultaneousl .

H rdcopy Output

The DSA524 can provide hardcop output via dot matrix printer

(Epson codes compatible, with a serial interface), a digital X-Y

plotter (HP-GL codes compatible, with a serial interface), an

analog X-Y plotter, or an analog Y-T chart recorder.

Because different users will wish to use different t pes of

printers or plotters, this subject cannot be usefull covered in

this tutorial. Please refer to the reference section of the manual

for a description of the PRINT and PLOT functions.

Remote Interf cing

The RS-423 serial interface (RS-232 compatible) and the

optional IEEE-488 interface of the DSA524 enable it to be

connected to a wide variet of other equipment. The interfaces

can be used for full remote control of the DSA (an thing that

can be controlled from the ke board can also be controlled via

the interfaces), and for bi-directional transfer of waveform data.

Refer to the reference section and appendices for full details.

A Fin l Word

This tutorial has covered most of the functions of the DSA524 in

terms of its use with a displa oscilloscope. The DSA524 is a

highl sophisticated and versatile instrument which has man

further uses which have not been touched upon in the tutorial,

in particular its use as an interfaceable and programmable

instrument. Some of its other facilities are covered in the

reference section of the manual, the appendices, or in individual

application notes.

APPENDICES

APPENDIX A. THE OSCILLOSCOPE DISPLAY

Single or du l c ble connection

The DSA524 produces a multiplexed output which enables two

traces plus text to be displa ed using onl one channel of the

displa oscilloscope. The multiplexed output also incorporates a

trigger signal. Consequentl the DSA can be connected to the

oscilloscope via just one cable with triggering being sourced from

the input channel.

The disadvantage of single cable connection is that the trigger

signal is visible at the left hand edge of the screen as a ver

narrow vertical pulse followed b a short bright line. Connecting a

second cable from the "Trig out" socket to the external trigger

input of the oscilloscope and setting the scope to external trigger

removes the visible trigger signal from the screen.

Triggering

Because the DSA524 produces a multiplexed output waveform,

trigger adjustment is ver important particularl when text is

being displa ed. If a satisfactor initial set-up displa cannot be

obtained check the following points:

The 'scope must be set to single channel operation. The input

coupling must be DC and the sensitivit must be set to

100mV/div. The sweep hold-off and trigger dela (if present)

must be set to minimum. The sweep speed must be set to

50us/div. The trigger source must be from the input channel (not

vertical mode). The trigger slope and level must both be

negative.

Adjust the trigger level. If a satisfactor displa can still not be

obtained tr setting the sweep speed to 20us/div and then slow-

ing it down to 50us/div using the sweep variable control.

When using a single cable connection, some oscilloscopes (those

having a poor d namic range on their trigger circuit) ma give

unstable triggering when full screen height waveforms are being

displa ed. Should this occur, first tr careful adjustment of the

trigger level control but if the trouble persists change to a two

cable connection.

Vertic l Size

The amplitude of the vertical output is factor adjusted to an

accurac of + 1 %. The two horizontal lines of the set-up displa

are intended to be exactl 6 divisions apart. The output level can

be adjusted to compensate for inaccuracies of the oscilloscope

using the rear panel preset adjustment marked "Set Height". If

the linearit of the oscilloscope is poor, however, it ma not be

possible to set the two lines at exactl ±3 divisions from the

arrow tip. If so ignore the vertical position of the arrow tip and

set the two lines to be at ±3 divisions from the graticule centre

line.

The horizontal timing of the DSA524 is cr stal controlled to an

accurac of 0.01% (except for "repeat" mode operation) and

cannot be adjusted.

APPENDIX B. ALIASING

One problem that occurs with digital storage oscilloscopes that

does not occur with real-time oscilloscopes is aliasing.

Sampling theor dictates that an periodic waveform must be

sampled at more than twice the highest frequenc component to

avoid aliasing. Aliasing causes the apparent waveform frequenc

to be much lower than the real frequenc . Thus if the timebase is

set too low an invalid displa will result (see Fig a).

To avoid aliasing the timebase must be set as follows:

Minimum time/div = 50 divided b the maximum c clic signal

frequenc .

The difficulties occur when the signal frequenc is unknown. In

this case it is safest to set a fast timebase speed initiall and

work down.

A second form of aliasing that can occur is visual aliasing. This

occurs when the displa is made up of bright dots and the

number of samples per waveform period is low (though greater

than two). The e e can be deceived into incorrectl linking the

dots to form a slower period waveform (see Fig b). The dot join

feature of the DSA524 greatl reduces the chances of visual

aliasing occurring.

Fig a. True aliasing -

waveform sampled at

less than twice the

signal frequenc (in

this case

approximatel at the

signal frequenc ).

Fig b Visual aliasing -

vertical separation

between samples

large in comparison

to horizontal separa-

tion, leading to incor-

rect interpretation b

the e e.

If the input signal is repetitive and the trigger repetition rate is

between 50Hz and 5MHz the AUTOSET function of the DSA524

can be used. Autoset resets the timebase to a speed suited to

the trigger rate and well above the point at which aliasing

effects can occur.

APPENDIX C. SINGLE-SHOT BANDWIDTH AND INTER-

POLATION

Probabl the most important use of a digital storage instrument

is for the capture of single-shot waveforms (i.e. waveforms

which occur onl once). The user will need to understand the

bandwidth restrictions which appl to this mode of operation.

N quist sampling theor dictates that a waveform can be per-

fectl re-constructed if sampled at more than twice the fre-

quenc of the highest frequenc component. Thus a 9.9 MHz

sinewave could be reconstructed if sampled at 20MHz. Unfortu-

natel this assumes that sampling can take place for an infinite

period of time. Clearl this is not possible with a single-shot

waveform.

In theor a single-shot waveform can onl be perfectl recon-

structed using an infinite sampling frequenc . This is because

the waveform has discontinuities at the start and end which

give rise to infinite frequenc elements. Given a known

maximum sampling frequenc we need to know how good a

representation of the original waveform can be achieved.

Because there can be no certaint of the existence of an c clic

elements in a single-shot waveform, sampling theor must be

abandoned. Instead, a subjective principle must be used to

decide what constitutes an acceptable representation of a

waveform. This will depend on the information that the user

needs to obtain from the waveform.

Consider the waveform of Fig c which consists of a rapid

change of level, followed b an exponential deca of sinusoidal

oscillations. If the user requires onl to know the settled

amplitudes before and after the change of level the sampling

frequenc requirements are modest since a representation

which merel indicates the disturbance and the settled values

will suffice.

However, if the user requires to know the rate of change of the

rising edge, the sampling frequenc requirements are consider-

able since a number of samples must be taken during the time of

the rise.

Fig c.

Most commonl , the user merel requires a representation of the

general shape of the waveform. In the case of the waveform of

Fig c it is clear that a reasonable representation can be obtained

using ten samples per c cle of the sinusoidal frequenc . This

leads to a useful rule of thumb which is that the sampling

frequenc should be at least ten times that of the fastest c clic

element in the waveform. Alternativel we could sa that the

single-shot bandwidth equals one tenth of the maximum

sampling frequenc .

Because a c clic element which is represented b ten samples

occupies onl 0.1 divisions on the displa , it will be necessar to

use "magnif " mode to view it properl . When the DSA524

displa mode is set to MAG it not onl increases the spacing

between the original samples b ten, but also calculates and dis-

pla s intermediate samples using mathematical interpolation.

The standard interpolation provided b the DSA524 is linear.

Linear interpolation joins the true samples with straight lines,

which improves the visual appearance of the waveforms when

the number of samples per c cle is low. Linear interpolation pro-

vides a good reconstruction of waveforms which are made up

mainl of linear elements.

The DSA524 also provides sine interpolation as an alternative.

This is based on a mathematical curve fitting algorithm known as

the "cubic spline", and provides an excellent reconstruction of

waveforms which appear to be made up of simple sinusoids. Sine

interpolation will provide a near perfect reconstruction of a

sinewave sampled at onl four samples per c cle.

This leads to a second useful rule of thumb which is that, when

using sine interpolation, the single-shot bandwidth equals one

quarter of the maximum sampling frequenc .

Sine interpolation will not provide a good reconstruction of the

parts of a waveform which are not smooth curves. It should

therefore not be used with pulse, triangle, sawtooth waveforms

etc.

APPENDIX D. ANALOG PLOTTER "PLOT" FUNCTION

The waveforms shown on the oscilloscope displa can be sent

either to an analog X-Y plotter or to a Y-T chart recorder using

the analog plotter interface.

The DSA is factor initialised for use with a digital plotter. To

change over to use with an analog plotter ke in "function 26"

(press FUNCTION NN, followed b 2 followed b 6). To return to

use with a digital plotter ke in "function 27".

The analog plotter interface is mounted on the rear panel and

has five 4mm sockets marked X, YA, GND, YB, and PL (pen lift).

The X signal is onl required when using an X-Y plotter. When

using a chart recorder the pen lift signal can be used to control

the chart movement.

The waveforms for Trace A and Trace B are sent simultaneousl

to their separate output sockets along with an X axis signal for

use with X-Y plotters. The 10.24 divisions of the displa are plot-

ted using a level of 100mV/div (for both Y and X) at a rate selec-

table as 1,2,5 or 10 seconds per division. The pen-lift signal is

normall "low to lift" but can be inverted.

To set the plot rate, press SHIFT (ke 8) followed b SET PLOT

(ke 5). The oscilloscope displa will show the present plot rate.

Press one of the REF CURS ke s (ke 2 or 3) to select a new

value, then press ESCAPE. If the DSA is not connected to an

oscilloscope the plot rate ma be set directl using the FUNC-

TION NN ke (see Section R27.).

Two versions of the PLOT function are provided. The default

version provides prompts for manual or semi-automatic

operation of the recorder or plotter. Its operation is as follows:

Before the PLOT function is commenced, the Y and X output

signals will both be at zero, representing the bottom left-hand

corner of the oscilloscope displa . The pen lift signal will be set

to "up".

Press PLOT (ke 6), the oscilloscope displa will show "ZERO

PEN/HIT ANY KEY". If RUN/HOLD was set to RUN it will become

set to HOLD. The interface will output YA and YB values

equivalent to + 4.25 divisions, and an X value equivalent to

+0.12 divisions. This represents the left-hand centre of the os-

cilloscope graticule. Adjust the zero controls of the plotter/re-

corder accordingl . The pen lift signal will remain set to "up".

Press an ke (e.g. PLOT), the displa will show "PEN DOWN/

HIT ANY KEY". The pen lift signal will be set to "down". If

automatic pen lift control is not being used, lower the pen.

Press an ke , the displa will show "PLOTTING". Plotting will

commence starting at X position 0.00 and continue to position

10.24. When plotting has finished the displa will show "PEN

UP/HIT ANY KEY". The pen lift signal will be set to "up". If

automatic pen lift control is not being used, raise the pen.

Press an ke , the Y and X output signals will both be set to

zero and the pen lift signal will remain "up". To abandon the

PLOT function at an stage before it is completed press

ESCAPE.

The alternative version of the PLOT function is intended for full

automatic control of the recorder/plotter. To change to this ver-

sion, ke in "function 25". To return to the normal prompted

version, ke in "function 26". The operation of the alternative

version is as follows:

Press PLOT (ke 6), the pen lift signal will be set to "down", and

plotting will commence starting at X position 0.00 and finishing

at 10.24. If RUN/HOLD was set to RUN it will become set to

HOLD. When plotting is completed, the pen lift signal will be set

to "up", and the Y and X output signals will both be set to zero.

To abandon plotting at an time press ESCAPE.

The Pen Lift signal has a level of either 0 volts or 5 volts from a

source impedance of 1K ohm. The default polarit of this signal

is "low to lift". This can be changed to "high to lift" b dismant-

ling the case and changing the jumper on the analog plotter

interface PCB from position 1 to position 2 (see diagram below).

The signal can be used to switch most logic based control

inputs including TTL. However it should not be connected to

input circuits which sink currents to below 0 volts or which

source currents of more than 1mA to a voltage above 5 volts.

Doing so could cause incorrect operation of the whole plotter

interface.

APPENDIX E. CONNECTING TO THE SERIAL INTERFACE

The interface uses a female 9-pin D connector and has five active

connections: pin 2 (RXD) is the data input line, pin (TXD) is the

data output line, pin 5 is signal ground, pin 8 (CTS) is the

hardware handshake input, pin 7 (RTS) is the hardware

handshake output. RTS can be disabled and forced permanentl

high b using FUNCTION 83 on the DSA, it can be re-enabled b

using FUNCTION 82.

Unfortunatel , although there are connection standards for

modems and for terminals, there is no single connection standard

appl ing to other equipment fitted with an RS-232C interface. It

will therefore be necessar to refer to the technical handbook of

the equipment concerned before a suitable connection cable can

be made up. The most commonl used connector s stem is a 25

pin "D" connector in a "terminal" configuration, and a suitable

cable wiring scheme for this is shown below.

Where bi-directional transfer of data is required, the TXD of the

DSA should be connected to the RXD of the other equipment and

the RXD of the DSA should be connected to the TXD of the other

equipment. Where unidirectional data transfer is required (i.e.

when connecting to a printer or plotter), the RXD of the DSA can

be left unconnected (unless X-ON/X-OFF handshaking is used).

Unless the baud rate is set ver low, some form of handshaking

connection will probabl be necessar . If hardware handshaking

is not being used, pin 8 (CTS) on the DSA cannot be left uncon-

nected and must be taken permanentl high. This can be done b

connecting pin 8 to pin 7 (RTS) and using FUNCTION 83 to force

RTS permanentl high. RTS can be re-enabled for normal

handshaking operation using FUNCTION 82.

Handshaking is necessar when the receiving equipment cannot

accept the data as fast as the sending device is sending it. Hand-

shaking allows the receiving device to tell the sending device

when to send data and when not to send data, thus controlling

the effective rate at which data is transmitted.

Handshaking is not alwa s needed. The receiving equipment ma

be able to keep up with the incoming data without needed to

interrupt it, either because the baud rate is set low enough that it

can act on the data as fast as it is being sent, or because it has a

large enough data-input buffer to accept all of the transmitted

data in one stream. However, even when a large data buffer is

available, handshaking can sometimes still be needed at high

baud rates because the RS-232 hardware of the equipment

cannot transfer data b tes into the buffer fast enough.

The DSA has a 40 b te data input buffer. When transmitting data

to the DSA baud rates up to 9600 can be used without

handshaking, above this handshaking will be needed for strings in

excess of 40 characters.

When making connection to a printer or plotter, the need for

handshaking will depend upon the characteristics of that device.

Because the amount of data transmitted is large (approx. 30K

b tes for a "print") the baud rate needs to be kept high to mini-

mise transmission time. Since the device is unlikel to have a

buffer large enough to accept the data in one stream, hand-

shaking will almost certainl be needed.

There are two basic t pes of handshaking, hardware handshak-

ing and X-ON/X-OFF handshaking. Both t pes are provided on

the DSA.

Hardware handshaking uses the RTS and CTS lines of the DSA.

When the RTS line is set to a 0 (a positive voltage level) the

DSA is read to receive data, when it is set to a 1 (a negative

voltage level) the DSA is not read to receive data. When CTS is

pulled to a 0 (positive) the DSA is enabled to send data, when it

is pulled to a 1 (negative) the DSA is disabled from sending

data.

X-ON/X-OFF handshaking uses the TXD line of the receiving

device to send messages to the transmitting device telling it to

stop or to start sending data. The X-OFF message (ASCII 13)

stops transmission, the X-ON command (ASCII 11) starts trans-

mission.

The protocol of the DSA is fixed (8 data bits, 1 start bit, 1 stop

bit, no parit ) and therefore an incompatibilit must be

removed b adjusting the protocol of the other equipment.

Most computers have full adjustable protocol but some

printers and plotters do not.

It is not essential to have exactl the same protocols on both

interconnected interfaces. The other interface must use 8 data

bits and 1 start bit, but parit can be even, odd or none, and

stop bits can be 1, 2 or more.

The wide range of baud rates available from the DSA should

ensure compatibilit with virtuall all equipment. Where the

other equipment also provides a choice of baud rates there are

a number of points to bear in mind when choosing which rate

to use.

Some t pes of equipment cannot handle incoming data at high

baud rates even when handshaking is correctl established.

Such problems are minimised at lower baud rates but waveform

data will take a long time to transfer. High baud rates will give

shorter transmission times but ma produce problems with

missing b tes.

APPENDIX F. SOFTWARE COMMANDS

The RS-423 and IEEE-488 interfaces provide identical facilities

for control and data transfer. The commands listed below are

common to both interfaces. The DSA is controlled b sending it

ASCII strings. Each string must be terminated with a carriage

return (shown in examples as CR). All commands are case sen-

sitive.

When the DSA receives a valid command string it responds b

sending back the string "OK CR". If the command string is not

valid the DSA responds b sending back the string "ERROR N

CR" where N is the number of the first apparentl invalid b te

of the command string.

1. Controlling the DSA front p nel set up.

For controlling the front panel, each ASCII string must consist

of a primar command followed b a comma followed b one or

more secondar commands (separated b commas) followed b

a carriage return.

There are seven primar commands for control of the front

panel. Each one defines a control area to which the secondar

command (or commands) will appl . The primar commands

are as follows:-

CH1 This defines the control area as channel 1

CH2 This defines the control area as channel 2

TRG This defines the control area as trigger

TMB This defines the control area as timebase

TRA This defines the control area as trace A

TRB This defines the control area as trace B

KEY This is a Global control command

For CH1 or CH2 the secondar commands are as follows:

2mV, 5mV, 10mV, 20mV, 50mV, 100mV, 200mV, 500mV, 1V,

2V, 5V, or 10V (This sets the input sensitivit .)

AC, DC or GND (This sets the input coupling.)

ZERO or VAR,N (where N is a number between -100 and

+100) (This sets the offset level equal either to zero or to N%

of its maximum value.)

OFF or ON (This turns the channel off or on.)

Example: CH 1,20mV, DC,VAR,50 CR

For TRG the secondar commands are as follows:

CH1, CH2 or EXT (This sets the trigger source.)

AUTO, NORM or LINE (This sets the trigger mode.)

POS or NEG (This sets the trigger slope.)

ZERO or VAR,N (where N is a number between -100 and

+100) (This sets the trigger level either to zero or to ±N% of

its maximum value.)

AC, DC or HFREJ (This sets the trigger coupling.)

EDLY,N (where N is a number between 0 and 15) (This sets

the trigger events dela .)

TDLY,N (where N is a number between -40 and 9999) (This

sets the trigger time dela .)

Example: TRG,CH2,AC,TDLY, -10 CR

For TMB the secondar commands are as follows:

50nS, 100nS, 200nS, or 500nS (This sets the timebase speed

in nanoseconds per division).

or 1uS, 2uS, 5uS, 10uS, 20uS, 50uS, 100uS, 200uS, or 500uS

(this sets the timebase speed in microseconds per division).

or 1mS, 2mS, 5mS, 10mS, 20mS, 50mS, 100mS, 200mS, or

500mS (this sets the timebase speed in milliseconds per

division).

or 1S, 2S, 5S, 10S, 20S, 50S, 100S, 200S or 500S (This sets

the timebase speed in seconds per division).

or 10M, 20M, 50M, 100M or 200M (This sets the timebase

speed in minutes per division).

COMP (This sets the SEARCH function into Compress mode).

SCAN,N (where N is a decimal number between 0 and 3100)

(This sets the SEARCH function into Scan mode with the trace

starting at word N).

MAG,N (where N is a decimal number between 0 and 900)

(This sets the SEARCH function into Magnif mode with the

trace starting at word N).

SROFF (This turns an of the SEARCH modes off).

NORM, SLOW or FAST (This sets the displa update rate).

ION or IOFF (This sets sine interpolation on or off).

AON or AOFF (This sets averaging on or off). Example:

TMB,10uS,AON,SLOW CR

For TRA or TRB the secondar commands are as follows:

HOME or VAR,N (where N is a number between -100 and

+100) (This sets the trace position either to "home" or to

N% of its maximum shift.)

CAL or UNCAL,N (where N is a number between 0 and 100)

CH1 or CH2 (This links the trace to CH1 (for TRA) or CH2

(for TRB).)

RCL,N (where N is a number between 1 and 16) (This

recalls a waveform to the displa from the corresponding

indexed memor .)

SAVE,N (where N is a number between 1 and 16) (This

memor .)

SAVE,N 'where N is a number between 1 and 161 (This

stores the waveform presentl displa ed on the trace into

the corresponding indexed memor .)

ADD or NOADD (TRCA onl ) (This turns the "add B to A"

function on or off.)

INV or NOINV (TRCB onl ) (This turns the trace invert func-

tion on or off.)

Example: TRA,HOME,UNCAL,40 CR KEY

KEY

The KEY command enables the front panel of the DSA to be

controlled in exactl the same manner as if the front panel ke s

were being pressed. This command provides for control of an

ke operated function including those not covered b the pre-

vious six primar commands (e.g. PLOT).

The primar command, KEY, must be followed b one or more

(maximum five) secondar commands each of which represents

a front panel ke . Each secondar command is a two or three

digit decimal code as shown on the diagram below.

Example: KEY,34,34,97 CR

This would have the effect of incrementing the CH1 volts/div b

two steps and decrementing the timebase time/div b one step.

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