Tektronix 7B80 User manual

Tektronix, lnc.
P.O. Box 500
Beaverton, Oregon 97077
INSTRUCTION MANUAL
Serial Number
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FIRST PRINTING NOV 1975

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7880 Operators
TABLE OF CONTENTS
PAGE PAGE
LIST OF ILLUSTRATIONS .................... ii
LIST OF TABLES ........................... ii
...
SAFETY SUMMARY ........................ 111
SECTION 1 OPERATING INSTRUCTIONS
INSTALLATIOIV ..................... 1-1
CONTROLS. CONNECTORS.
AND INDICATORS
................. '. .. 1-1
FUNCTIONAL CHECK
................. 1-1
Setup Procedure
.................... 1-1
Sweep Functions
.................... 1-4
Triggering Functions
................. 1-4
GENERAL OPERATING INFORMATION
.... 1-5
Triggering Switch Logic
............... 1-5
.................... Triggering Modes 1-5
Trigger Coupling
.................... 1-6
Trigger Source
..................... 1-6
Trigger Slope
...................... 1-7
Trigger Level
...................... 1-7
Horizontal Sweep Rates
............... 1-7
Time Measurement
.................. 1-7
Sweep Magnification
................. 1-7
Variable Hold Off
................... 1-7
Mainframe Operating Modes
............ 1-9
............
REPACKAGING FOR SHIPMENT 1-9
APPLICATIONS
........................ 1.10
TIME-INTERVAL MEASUREMENTS
....... 1.10
....... Period and Frequency Measurements 1.10
..... Rise-Timeand Fall-TimeMeasurements 1.11
............. Pulse Width Measurements 1.12
DELAYED-SWEEPMEASUREMENTS
....... 1.12
X-Y PHASE MEASUREMENTS
............ 1.12
SECTION
2 SPECIFICATION
STANDARD ACCESSOR lES
............. 2-3
SECTION 3 INSTRUMENT OPTIONS
b
REV . A. SEPT . 1977
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7880 Operators
LlST OF ILLUSTRATIONS
FIGURE
NO. PAGE
Frontispiece.
..................... iv
1-1 Location of release latch.
............ 1-1
1-2 Front-panelcontrols, connectors,
and indicators.
................... 1-2
1-3 Effectof LEVELcontroland SLOPE
switch oncrt display
............... 1-8
1-4 Area of graticule used for most accurate
time measurements
................ 1-9
FIGURE
NO. PAGE
1-5 Operation of sweep magnifier
......... 1-9
1-6 Measuringthe periodanddetermining
the frequency of adisplayedwaveform
.. .I-10
1-7 Measuringthe rise time and fall time of
adisplayedwaveform.
............. .l-11
1-8 Measuringthe pulse width of adisplayed
waveform.
..................... .l-12
2-1 7B80dimensional drawing
........... 2-3
LlST OF TABLES
TABLE
NO.
TABLE
PAGE
NO.
PAGE
............. 2-1 Electrical Characteristics. ............ 2-1 2-3 Physical Characteristics. 2-3
2-2 Environmental Characteristics
......... 2-3
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7B80 Operators
This manualcontainssafety information which the user must follow to ensure safe operationof this instrument.WARNING
information
is intendedto protect the operator, CAUTION information is intended to protectthe instrument. The following
are general safety precautions that must be observedduring
all phases of operation.
1 WARNING 1
Ground the Instrument
Toreduce electrical-shockhazard, the mainframe (oscilloscopelchassis must be properly grounded. Refer to the mainframe
manual for grounding information.
Do Not Operate in ExplosiveAtmosphere
Do not operate this instrument in an area where flammablegases or fumes are present. Such operation could cause an
explosion.
Avoid Live Circuits
Electrical-shockhazardsarepresent in thisinstrument. Theprotective instrument coversmust not be removed by operating
personnel. Component replacement and internal adjustmentsmust be referred to qualified servicepersonnel.
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7B80 Operators
7B80 Features
The 7B80 Time-Base unit providescalibrated sweep rates from 5 secondsto 10nanoseconds and triggering to400 megahertz
for 7700-, 7800-, and 7900-seriesoscilloscopes. A XI0Magnifier increases each sweep rate by a factor of 10and a VARI-
ABLE TIMEIDIV control providescontinuously variable sweep rates betweencalibrated steps. Variable holdoff and alpha-
numeric readout are provided. Also, when operating inthe AUTO TRIGGERING MODE, a bright baseline trace
is displayed
inthe absence of atrigger signal. The 7880 can be operated as an independent time base or as a delayed-sweepunitwith acom-
panion delaying time-baseunit.
@
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Section 1-7880
The 7680 Time-Baseunitoperates with a Tektronix 7700-, 7800-,and 7900-seriesoscilloscope mainframes and a 7A-series
amplifier unit toform acompleteoscilloscopesystem. This section describes the operation of the front-panel controls and
connectors, providesgeneral operating information, afunctional check procedure, and basic applications for this instrument.
INSTALLATION
The time-base unit is designed tooperate inthe horizontal
plug-in compartment of the mainframe. This instrument
can also be installedin
a vertical plug-in compartment to
provide
a vertical sweep on the crt. However, when used in
this manner, there are no internal triggering or retrace
blanking provisions, and the unit may not meet the specifi-
cations given inSection 2.
To install the unit in
a plug-incompartment, push it inuntil
it fits firmly intothe compartment. The front panel of the
unitshould be flush with the front panel of the mainframe.
Even though the gain of the mainframe
is standardized,the
sweep calibration of the unitshould be checkedwhen in-
stalled. The procedure for checking the unit is given under
Sweep Functions in the Functional Check procedure inthis
section.
To remove the unit, pull the release latch (see Figure 1-1)
todisengage the unit from the mainframe, and pull
it out of
the plug-in compartment.
CONTROLS, CONNECTORS, AND INDICATORS
All controls, connectors, and indicators required for the
operation of the time-base unit are located on the front
panel. Figure 1-2shows and provides
a brief description of
all front-panel controls, connectors, and indicators. More
detailed information is given in the General Operating
Instructions.
FUNCTIONALCHECK
The following procedures are provided for checkingbasic
instrument functions. Refer tothe description of the con-
trols, connectors, and indicators while performing this pro-
cedure. If performing the functional check procedure
reveals
a malfunction or possible improper adjustment, first
check the operation of the associated plug-in units, then re-
fer tothe instruction manual for maintenanceand adjust-
ment procedures.
Setup Procedure
1. Install the time-base unit being checked inthe A hori-
zontal compartment of the mainframe.
2. Install an amplifier plug-in unit inavertical compart-
ment.
3. Set the time-base unit controls as follows:
SLOPE
MODE
COUPLING
SOURCE
POSITION
TIMEIDIV
VARIABLE
(CAL IN)
HOLDOFF
MAG
(+I
P-PAUTO
AC
INT
Midrange
1ms
Calibrated (Pushed in)
MIN (fullycounter-
clockwise)
XI (pushed in)
4. Turn on the mainframeand allow at least 20 minutes
warmup.
RELEASE
LATCH
1958-3
Fig. 1-1. Location of release latch.
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Operating Instructions-7B80
Fig. 1-2. Front-panel controls, connectors, and indicators.
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OperatingInstructions-7B80
TRIGGERING
@ LEVELControl-Selects a point onthe trigger signal where triggering occurs.
@) SLOPE Switch-Permits sweep tobetriggeredon negativeor positiveqoing portionsof the trigger signal.
@ READY Indicator-Illuminates when sweep circuit is armed (SINGLESWEEP Mode).
@ TRIG'D Indicator-Illuminates when thedisplay istriggered.
@ MODE Pushbunons-Selects the operating mode of thetriggering circuit.
@ COUPLING PushbunonrSelects the method of coupling the trigger signal totriggering circuit.
@ SOURCE Pushbunons-Selects source of the trigger signal.
SWEEP
@ POSITION Control-Provides horizontal positioning.
@ FINEControl-Provides precisehorizontal positioning.
@ MAGPushbunon-Selects magnified XI0or unmagnified sweep.
@ WOLD OFF Control-Permits holdoff periodto be variedtoimprove trigger stability on repetitivecomplex waveforms.
@ TlMElDlV Selector-Selects thesweep rate of the weep generator.
13
VARIABLE Control andCALSwitch--Selectscalibrated or uncalibrated sweep rates. Uncalibrated sweep ratescan
O ba continuously reduced toat least thesweep rateof thenext dower position.
@ SWP CALAdjustment-Compensates for basic timingchanges due tothedifferences insensitivity of mainframes
EXTERNAL TRIGGER INPUT
@ EXTTRlG ATTENUATOR-Selects attenuationfector for external trigger signals.
@ EXTTRlG INConnector-Connector (BNCtype) provides inputfor external trigger signals.
Fig. 1-2. Front-panel controls, connectors, and indicators (cont.).
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Operating Instructions-7B80
5. Set the mainframe vertical and horizontal modes todis-
play the plug-in units used and adjust the intensity and
focus for awell-defined display. See the oscilloscopemain-
frame and amplifier unit instruction manuals for detailed
operating instructions.
Sweep Functions
NORMALSWEEP. Perform the following proceduretoob-
tain a normal sweep and to demonstrate the function of the
relatedcontrols:
2. Press to releasethe MAG button (X10). Notethat the
unmagnified display within the center division of the grati-
cule is magnified toabout 10divisions.
3. Press the MAG button (XI
).
Triggering Functions
Perform the following procedure to obtain a triggered
sweep and to demonstrate the functions of the related
controls:
1. Perform the precedingSetup Procedure. 1. Obtain adisplay as described inthe precedingNormal
Sweep procedure.
2. Connect a 0.4-volt, l-kilohertz signal from the main-
frame calibrator tothe amplifier unit input.
3. Set the amplifier unit deflection factor for 4 divisions of
display.
4. Adjust the LEVELcontrol for astable display.
5. Turn the POSITION control and note that the trace
moves horizontally.
6. Turn the FINEcontrol and note that the display can be
precisely positioned horizontally.
7. Check the display for one complete cycle per division. If
necessary, adjust the front-panel SWP CALscrewdriver ad-
justment for one complete cycle per division over the
center 8 graticule divisions. Be sure that the timing of the
mainframe calibrator signal
is accurate to within 0.25%
(+20 to+30° C).
8. Press to release the VARIABLE (CAL IN)control. Turn
the VARIABLE (CAL IN)control fully counterclockwise
and notethat the displayed sweep rate changes toat least
the next slower TIMEIDIV switch setting (i.e., 2 milli-
secondsldivision). Press the VARIABLE (CAL IN)knob in
tothe calibrated position.
MAGNIFIEDSWEEP. Perform the following procedure to
obtain a XI0 magnified display and to demonstrate the
function of the related controls:
1. Obtain aone cycle per division display as described in
the precedingNormal Sweep procedure.
2. Press the AUTO MODE button and turn the LEVEL
control fully counterclockwise to obtain a free-running
sweep.
3. Slowly turn the HOLD OFF control clockwise and note
that astable display can be obtained at several positions of
the HOLD OFF control. Return the HOLDOFF control to
the fully counterclockwise (MIN)position.
NOTE
TheHOLD OFF control varies thesweep hold-off
time which effectively changes therepetition-rate
of thehorizontal sweep signal. However, itspri-
mary function is toobtain astable display of
complex waveforms which are otherwise difficult
to trigger.
4. Press the AC, AC HF REJ, and DC COUPLING buttons
for boththe
+ and - positionsof the SLOPE switch and
check for astable display (LEVELcontrol may be adjusted,
if necessary, toobtain astable display).
5. Apply the 0.4-volt, 1 kilohertz signal from the main-
frame calibrator tothe amplifier unit and tothe EXTTRIG
INconnector.
6. Press the EXTSOURCE buttonand set the amplifier
unit deflection factor for a4-division display.
7. Press the AC, AC HF REJ, and DC COUPLING buttons
for boththe
+ and - positions of the SLOPE switch and
check for astable display (LEVELcontrol may be adjusted,
if necessary, for astable display).
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OperatingInstructions-7B80
8. Press the AC COUPLING, INTSOURCE, and NORM
MODE buttons. Adjust the LEVEL control for a stable
display.
9. Press the AUTO MODE button and adjustthe LEVEL
control for afree-runningdisplay.
10. Press the NORM MODE button and check for no
display.
11. Adjust the LEVEL control for a stable display and
press the SINGLE SWP MODE button.
12. Notethat one trace occurswhen the RESETMODE
button
is pressed.
13. Disconnectthe mainframecalibrator signal from the
amplifier unit input and press the RESET MODE button.
Check for no display and note that the READY indicator
is lit.
14. Notethat one trace occurs and that the READY indi-
cator extinguisheswhen the mainframecalibrator signal
is
reconnectedtothe amplifier unit input.
GENERAL OPERATING INFORMATION
Triggering Switch Logic
The MODE, COUPLING, and SOURCE push buttons of the
TRIGGERING switches are arranged inasequence which
places the most-oftenused position at the top of each series
of push buttons. With this arrangement, astable display can
usually be obtained by pressingthe top push buttons: P-P
AUTO, AC, INT. When an adequate trigger signal is applied
and the LEVEL control is correctly set, the unit
is triggered
as indicated by the illuminated TRIG'D light. If the
TRIG'D light
is not on, the LEVELcontrol is either at a
settingoutside the range of the trigger signal applied tothis
unitfrom the vertical unit, the trigger signal amplitude
is in-
adequate, or its frequency is below the lower frequency
limitof the AC COUPLING switch position. Ifthe desired
display
is not obtained with these buttons pushed in, other
selections must be made. Refer tothe following discussions
or the instruction manualsfor the associated oscilloscope
mainframe and vertical unit(s) for more information.
Triggering Modes
The MODE push-button switches select the mode in which
the sweep
is triggered.
P-P AUTO. The P-P AUTO MODE provides a triggereddis-
play at any setting of the LEVEL control whenever an ade-
quate trigger signal
is applied. The range of the LEVEL
control inthe P-PAUTO MODE
is between approximately
10%and 90%of the peak-to-peakamplitude of the trigger
signal. The LEVELcontrol can be set so that the displayed
waveform starts
at any point within this range on either
slope. The trigger circuits automatically compensate for a
change intrigger-signalamplitude. Therefore, ifthe LEVEL
control
is set tostart the waveform displayat acertain per-
centage point on the leadingedge of a low-amplitudesignal,
it triggersat the same percentage point on the leadingedge
of a high-amplitude signal if the LEVEL control
is not
changed. When the trigger repetition rate
is outside the
parameter given in the Specification section, or when the
trigger signal
is inadequate, the sweep free runs at the rate
indicated by the TIME/DIV switch to produce a bright
base-linereferencetrace (TRIG'D light off). When an ade-
quate trigger signal
is again applied, the free-runningcondi-
tion ends and atriggered display
is presented.
The P-PAUTO MODE
is particu!arly useful when observing
aseries of waveforms, since
it is not necessary toresetthe
LEVEL control for each observation. The P-P AUTO
MODE is used for most applications because of the ease of
obtaining a triggered display. The AUTO, NORM, and
SINGLE-SWP MODE settings may be used for special
applications.
AUTO. The AUTO MODE provides a triggered display
with the correct setting of the LEVELcontrol whenever an
adequatetrigger signal
is applied (see Trigger Level discus-
sions). The TRIG'D light indicates when the display
is
triggered.
When the trigger repetition rate
is outside the frequency
range selected by the COUPLING switch or the trigger sig-
nal
is inadequate, the sweep free runsat the rate indicated
by the TIME/DIV switch (TRIG'D indicator off). An ade-
quate trigger signal ends the free-runningcondition and
a
triggered display is presented. The sweep also free runs at
the rate indicated by the TIMEIDIV switch when the
LEVELcontrol
is at asettingoutside the amplitude range
of the trigger signal. This type of free-running display
is
usefulwhen it is desired tomeasure only the peak-to-peak
amplitude of a signal without observing the waveshape
(such as bandwidthmeasurements).
NORMAL. The NORM MODE provides atriggered display
with the correct setting of the LEVELcontrol whenever an
adequate trigger signal
is applied. The TRIG'D light indi-
cates when the display is triggered.
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Operating Instructions-7B80
The normal trigger mode must be used to producetriggered
displayswith trigger repetition rates below about 30 hertz.
When the TRIG'D light
is off, no trace is displayed.
SINGLE SWEEP. When the signal to be displayed
is not re-
petitive or varies inamplitude, waveshape, or repetition
rate, aconventional repetitive type display may produce an
unstablepresentation. Under these circumstances, astable
displaycan often
be obtained by usingthe single-sweep
featureof this unit. The single-sweepmode
is also usefulto
photograph non-repetitive or unstabledisplays.
To obtain
a single-sweep display of a repetitive signal, first
obtainthe best possible display inthe NORM MODE. Then,
without changing the other 'TRIGGERING controls, press
the SINGLE SWP RESET button. A single trace
is present-
ed each time this button
is pressed. Furthersweeps cannot
be presented until the SINGLE SWP RESET button
is pres-
sed again. If the displayed signal
is a complex waveform
composed of varying amplitude pulses, successive single-
sweep displays may not start at the same point on the wave-
form. To avoid confusion due tothe crt persistence, allow
the display todisappear before pressingthe SINGLE SWP
RESET button again. Atfast sweep rates,
it may be diffi-
cult to view the single-sweep display. The apparent trace
intensity can be increased by reducingthe ambient light
level or by using a viewing hood
as recommended in the
mainframeinstruction manual.
When using the single-sweepmode to photograph wave-
forms, the graticule may have to be photographed
separately inthe normal mannerto prevent over exposing
the film. Be sure the camera system
is well protected
against stray light, or operate the system in
a darkened
room. For repetitive waveforms, press the SINGLE SWP
RESET buttononly once for each waveform unlessthe sig-
nal
is completely symmetrical. Otherwise, multiple wave-
forms may appear on the film. For random signals, the lens
can be left open untilthe signal triggers the unit. Further
information on photographic techniques is given in the
appropriatecamera instruction manual.
Trigger Coupling
The TRIGGERING COUPLING push buttons select the
method inwhich the trigger signal
is connected tothe trig-
ger circuits. Each position permitsselection or rejection of
some frequency components of the signal which triggers
the sweep.
AC. AC COUPLING blocksthe dc component of the trig-
ger signal. Signals with low-frequency components below
about 30 hertz are attenuated. Ingeneral, AC COUPLING
can be used for most applications. However, ifthe signal
containsunwantedfrequency componentsor ifthe sweep
is
tobe triggered at alow repetition rateor dc level, one of
the other COUPLING switch positionswill provide
a better
display.
AC
LF REJ. AC LF REJCOUPLING rejectsdc, and atten-
uates low-frequency trigger signals below about 30 kilo-
hertz. Therefore, the sweep
is triggered only by the higher-
frequency components of the trigger signal. This position is
particularly usefulfor providingstable triggering ifthe trig-
ger signal contains line-frequency components. Also, the
AC LF REJ position providesthe best alternate-modeverti-
cal displays
at fast sweep rates when comparing two or
more unrelatedsignals.
AC
HF REJ. AC HF REJ COUPLING passes all low-
frequency signals betweenabout 30 hertz and 50 kilohertz.
Dc
is rejectedand signals outside the above range are atten-
uated. When triggering from complex waveforms, this posi-
tion
is useful to provide a stable display of the low-
frequency components.
DC. DC COUPLINGcan be used to provide stable trigger-
ingfrom low-frequency signals which would be attenuated
inthe other COUPLING switch positions. DC COLlPLlNG
can be used to trigger the sweep when the trigger signal
reaches
a dc level set by the LEVEL control. When using
internal triggering, the settingof the vertical unit position
control affects the triggering point.
Trigger Source
The TRIGGERING SOURCE push buttons select the
source of the trigger signal which
is connected tothe trigger
circuits.
INTERNAL. The INT position connects the trigger signal
from the vertical plug-in unit. Further selection of the in-
ternal trigger signal may be provided by the vertical plug-in
unitor by the mainframe; see the instruction manualsfor
these instrumentsfor more information. For most applica-
tions, the internal source can be used. However, some
applications requirespecial triggeringwhich cannot be ob-
tained inthe INTposition. Insuch cases, the LlNE or EXT
positionsof the SOURCE switches must be used.
LINE. The LlNEposition connects
a sample of the power-
line voltage from the mainframetothe triggercircuit. Line
triggering
is useful when the input signal is time-related
(multipleor submultiple)tothe line frequency.
It is also
useful for providing a stable display of a line-frequency
component inacomplex waveform.
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Operating Instructions-7B80
EXTERNAL. The EXT position connectsthe signal from
the EXTTRIG INconnector tothe trigger circuit. The ex-
ternal signal must be time-relatedto the displayed wave-
form for astable display. An externaltrigger signal can be
used toprovideatriggereddisplay when the internal signal
is either too low inamplitude for correct triggeringor con-
tains signal componentson which triggering is not desired.
It is also useful when signal tracing in amplifiers, phase-shift
networks, wave-shaping circuits, etc. The signal from a
single point in the circuit can be connected to the EXT
TRIG INconnector through a probe or cable. The sweep
is
then triggered by the same signal at all times and allows am-
plitude, time relationship,or waveshape changes of signals
at various points inthe circuit to be examined without re-
settingthe TRIGGERING controls.
The+10 push buttonattenuates the externaltrigger signal
by afactor of 10. Attenuation of high amplitude external
trigger signals
is desirable toincreasethe effective range of
the LEVELcontrol.
Trigger Slope
The TRIGGERING SLOPE switch (concentricwith the
TRIGGERING LEVEL control) determines whether the
trigger circuit responds on the positive- or negative-going
portion of the trigger signal. When the SLOPE switch
is in
the
(+) (positive-going)position, the display starts on the
positive-going portion of the waveform (see Figure 1-3).
When several cycles of asignal appear inthe display, the
setting of the SLOPE switch
is often unimportant. How-
ever, ifonly acertain portion of acycle
is to be displayed,
correct settingof the SLOPE switch
is important to provide
adisplay that starts on the desiredslope of the input signal.
Trigger Level
The TRIGGERING LEVELcontrol determinesthe voltage
level on the trigger signal at which the sweep
is triggered.
When the LEVELcontrol
is set inthe + region, the trigger
circuit respondsat amore positivepoint on the trigger sig-
nal.When the LEVEL control
is set inthe - region, the
trigger circuit responds at a more negative point on the
trigger signal. Figure 1-3illustratesthis effect with different
settings of the SLOPE switch.
To set the LEVELcontrol, first select the TRIGGERING
MODE, COUPLING, SOURCE, and SLOPE. Then set the
LEVELcontrol fully counterclockwiseand rotate
it clock-
wise untilthe display starts at the desired point.
Horizontal Sweep Rates
The TIMEIDIV switch providescalibratedsweep rates from
5 seconds/division to 10 nanoseconds/division in a 1-2-5
sequence. The VARIABLE TIMEIDIV control must be in
the calibratedposition and the MAG switch set to XI to
obtain the sweep rate indicated by the TIMEIDIV switch.
However, the mainframecrt readoutwill display the appro-
priate sweep rate.
The VARIABLE TIMEIDIV control includesatwo-position
switch todetermine if the sweep rate
is calibrated, or un-
calibrated. When the VARIABLE control
is pressed in, it is
inoperative and the sweep rate is calibrated. When pressed
and released outward, the VARIABLE control
is activated
for uncalibratedsweep rates, toat least the sweep rate of
the next slower position.
A calibratedsweep rate can be obtainedinany position of
the VARIABLE control by pressingin the VARIABLE con-
trol. This feature
is particularly usefulwhen aspecific un-
calibrated sweep rate has been obtainedand
it is desiredto
switch between calibrated and uncalibrated displays.
Time Measurement
When makingtime measurements from the graticule, the
area betweenthe second and tenth vertical lines of the gra-
ticule provides the most linear time measurements (see
Figure 1-4).Position the start of the timing area to the
second vertical lineand adjust the TIMEIDIV switch so the
end of the timing area falls between the second and tenth
vertical lines.
Sweep Magnification
The sweep magnifiercan be used to expand the display by a
factor of 10. The center division of the unmagnifieddisplay
is the portionvisible on the crt inthe magnifiedform (see
Figure 1-5).The equivalent length of the magnifiedsweep
is
more than 100 divisions; any 10 division portion can be
viewed by adjustingthe POSITIONand FINE POSITION
controls tobringthe desired portion intothe viewing area.
When the MAG switch
is set toXI0(OUT)the equivalent
magnifiedsweep rate can be determined by dividing the
TIMEIDIV settingby 10; the equivalent magnifiedsweep
rate
is displayedon the crt readout.
Variable Hold Off
The HOLDOFF control improves triggeringstability on re-
petitive complex waveforms by effectively changing the
repetition rate of the horizontal sweep signal. The HOLD
OFF control should normally be set to
its minimum setting.
When astable display cannot be obtainedwith the TRIG-
GERING LEVELcontrol, the HOLDOFF control can be
varied for an improveddisplay. Ifastable display cannot be
obtainedat any settingof the LEVELand HOLD OFF con-
trols, check the TRIGGERING COUPLINGand SOURCE
switch settings.
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Operating Instructions-7B80
TRIE'D
DLQCE
LEVEL
(SLOPE)
(LEVEL)
CRT DISPLAY
OBTAINED WlTH
SLOPE SWITCH
SET TO POSITIVE(+)
TRIE'D
DLQPI
LEVEL
CRTDISPLAY
OBTAINED WlTH
SLOPE SWITCH
SET TO NEGATIVE
(-)
TRIE'D
DLQCI
LEVEL
Fig. 1-3. Effect of LEVELcontrol and SLOPE switch on crt display.
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Operating Instructions-7B80
Mainframe Operating Modes
The time-base unit can be operated either as an indepen-
dent time base in any Tektronix 7700-, 7800-, or 7900-
series oscilloscopemainframe, or as adelayed-sweepunit in
those mainframesthat have two horizontal compartments.
A companion delayingtime-baseunit is requiredfor delayed-
sweep operation. Refer tothe delaying time-base unit in-
struction manual for additional information.
SECOND-VERTICAL TENTH-VERTICAL
LINE LINE
I
I
I I
p-TIME MEASUREMENT -4
AREA
C1752-06
Fig. 1-4. Area of graticule used for most accurate time measure-
ments.
REPACKAGING FOR SHIPMENT
If the Tektronix instrument is to be shipped to aTektronix
Service Center for service or repair, attach a tag showing:
owner (with address) and the name of an individual at your
firm that can be contacted, complete instrument serial
number and adescription of the service required.
Save and re-use the package in which your instrument was
shipped. If the original packaging is unfit for use or not
available, repackagethe instrument as follows:
Fig. 1-5. Operation of sweep magnifier.
Surround the instrument with polyethylene sheeting to
protect the finish of the instrument. Obtain a carton of
corrugated cardboard of the correct carton strength and
having inside dimensions of no less than six inches more
than the instrument dimensions. Cushion the instrument
by tightly packing three inches of dunnage or urethane
foam between carton and instrument, on all sides. Seal
carton with shipping tape or industrial stapler.
The carton test strength for your instrument
is 200 pounds.
REV. A, SEPT. 1977
Scans by ArtekMedia O 2006
ArtekMedia
Digitally signed by ArtekMedia
DN: cn=ArtekMedia, o=ArtekMedia.com, ou,
[email protected], c=US
Date: 2008.11.17 09:29:57 -06'00'

OperatingInstructions-7B80
APPLICATIONS
The following information describes proceduresand techniques for makingbasic time measurementswith the time-baseunit
installedin
a Tektronix 7700-, 7800-, or 7900-series oscilloscope. These procedures provide enoughdetail toenable the
operator to adapt them to other related time measurements. Contact your Tektronix Field Office or representative for
assistance inmakingmeasurementsthat are not described inthis manual.
TIME-INTERVAL MEASUREMENTS
Since time is a function of the sweep rate and the horizon-
tal distance (indivisions)that the sweep travels across the
graticulein
a calibrated-sweeposcilloscope system, the time
interval between any two points on a waveform can be
accurately measured. The following procedures provide
methods to measure some of the more common time-
related definable characteristics of a waveform such
as
period, frequency, rise time, fall time, and pulse width. The
procedurefor each of these measurements
is essentially the
same, except for the points between which the measure-
ments are made. The time interval between any two
selected points on adisplayedwaveform can be measured
with basicallythe same technique.
Period and Frequency Measurements
7. Measure the horizontal distance indivisions over 1com-
plete cycle of the displayed waveform (see Figure 1-61.
8. Multiply the horizontaldistance measured inStep 7 by
the TIME/DIV switch setting. (Dividethe answer by 10 if
sweep magnification is used.)
Example: Assume that the horizontal distance over 1com-
pletecycle
is 7divisions, and the TIMEIDIV switch setting
is .1 ms (see Figure 1-6).
Usingthe formula:
Period
= Horizontal distance X TIMEIDIV setting
Magnification
Performthe following proceduretomeasure the period and
determine the frequency of
a displayedwaveform: Substituting values:
1. Install the time-base unit in
a mainframe horizontal Period
= 7 X 0.1 ms = 0.7 millisecond
compartment (eitherA or B horizontal inafour-compart- 1
ment mainframe).
2. Connectthe signalto be measuredtothe vertical unit
input.
3. Set the mainframe horizontal- and vertical-modeswitch-
es todisplay the time base and vertical units. (Check that
the time base VARIABLE (CAL IN)control
is pushed in
and the HOLD OFF control
is inthe MIN position.)
4. Set the TRIGGERING switches and LEVEL control for
a stable display (see General Operating Information for
selecting propertriggering).
5. Set the vertical deflection factor and position control
for about a 5-divisiondisplay, vertically centered on the
graticule.
6. Set the TIMEIDIV switch and POSITIONcontrol for 1
completecycle displayedwithin the center 8 graticuledivi-
Fig. 1-6. Measuringthe period and determiningthe frequency of a
sions as shown in Figure 1-6.
displayedwaveform.
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OperatingInstructions-7B80
9. Determine the frequency of the displayedwaveform ob-
tained insteps 1through
8 by taking the reciprocal of the
periodof 1cycle.
Example: Assume that the periodof the displayed wave-
form
is 0.7 millisecond.
Usingthe formula:
Frequency
= 1
Period
Substituting values:
Frequency
= 1 = 1.43 kilohertz
0.7 ms
Rise-Timeand Fall-Time Measurements
Performthe following procedureto measure the rise time
and fall time of adisplayed waveform:
1. Install the time-base unit in a mainframe horizontal
compartment (eitherA or B horizontal inafour-compart-
ment mainframe).
2. Connect the signal to be measuredtothe vertical unit
input.
RISE TlME
10
9
1'
FALLTlME
1
1985-11
3. Set the mainframehorizontal- and vertical-modeswitch-
es to display the time base and the vertical unit. (Check
that the time base VARIABLE (CAL IN)control
is pushed
in and the HOLD OFF control
is in the MIN position.)
Fig. 1-7. Measuringthe rise time and fall time of a displayed wave
form.
4. Set the TRIGGERING switches and LEVELcontrol for
a stable display (see General Operating lnformation for
selecting proper triggering). or falling portion of the waveform that
is 10%and the
point that
is 90%of the total display amplitude (see Figure
1-7).
5. Set the vertical deflection factor and position control
for avertically-centereddisplay with an exact number of
divisions of amplitude. NOTE
6. Set the TIMEIDIV switch and POSITION control todis-
play the risingor falling portion of the waveform within the
center
8 graticule divisions as shown in Figure 1-7 (see
General Operating lnformation inthis section for discussion
of timingmeasurementaccuracy).
Theleft edge of the oscilloscope graticule is
scribed with 0, 10,90,and 100% lines for con-
venience when measuring rise time or fall time.
Touse this feature,adjust the vertical deflection
factorand position control to fit thedisplay be-
tween the0 and 100%graticule lines. Then
measure thehorizontal distance between the
points where the waveform crosses the 10%and
90%graticule lines.
7. Determinerisetime or fall time by measuringthe hori-
zontal distance indivisions betweenthe point on the rising
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Operating Instructions-7B80
8. Multiply the horizontal distance measured in step 7 by
the TIMEIDIV switch setting. (Dividethe answer by 10if
sweep magnification
is used.)
Example: Assume that the horizontal distance from the 10
to90% points
is 2.5 divisionsand the TIMEIDIV switch set-
ting
is .l ps (see Figure 1-7).
Usingthe formula: Horizontal distance TIMEIDIV
Rise Time = (divisions) setting
Magnification
Substituting values:
Rise Time
= 2.5 x 0.1 ps = 0.25 microsecond
8. Multiply the horizonal distance measured instep 7 by
the TIMEIDIV switch setting. (Dividethe answer by 10 if
sweep magnification
is used.)
Example: Assume that the horizontal distance between the
50%amplitude points
is 3 divisions, and the TIMEIDIV
switch setting is .l ms (see Figure 1-8).
Usingthe formula: Horizontal TIMEIDIV
Pulse Width = distance X
setting
Magnification
Substituting values:
Pulse Width
= 3 X 0.1 ms = 0.3 millisecond
1
DELAYED-SWEEPMEASUREMENTS
Pulse Width Measurements
Perform the following procedure to measure the pulse
width of adisplayed waveform:
1. Install the time-base unit in a mainframe horizontal
compartment (either A or Bhorizontal in afour-compart-
ment mainframe).
2. Connectthe signal tobe measuredto the vertical unit
input.
The time-baseunit may be used with adelaying time-base
unitin a mainframewith two horizontal compartments to
make delayed-sweep measurements. See the Tektronix
ProductsCatalog for compatibledelayingtime-base plug-in
units. Ifacompatibledelaying time-baseunit
is available,
refer to the instruction manual for that unit for detailed
delayed-sweepmeasurement procedures.
X-Y PHASE MEASUREMENTS
The phase difference betweentwo signals with the same fre-
quency can be measured with a 7B80Option 2 and ampli-
fier plug-inunits. Refer tothe Instrument Optionssection
of this manual for detailed procedures.
3. Set the mainframe horizontal- and vertical-mode
switchestodisplay the time base and vertical unit. (Check
that the time base VARIABLE (CAL IN)control
is pushed
in and the HOLD OFF control
is in the MIN position.)
4. Set the TRIGGERING switches and LEVEL control
for astable display (see General Operating Information for
selecting propertriggering).
5. Set the vertical deflection factor and position control
for about a 5-division pulse vertically centered on the
graticule.
6. Set the TIMEIDIV switch and POSITIONcontrol for 1
complete pulse displayed within the center 8 graticule divi-
sions as shown in Figure 1-8.
7. Measurethe horizontal distance in divisions betweenthe
50% amplitude points of the displayed pulse (see Figure
1-8).
Fig. 1-8. Measuringthe pulse width of a displayedwaveform.
PULSE WIDTH
1
AT06
1985-12
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Section2-7B80
SPECIFICATION
This instrument will meet the electricalcharacteristics listed inTable 2-1, following completeadjustment.The following elec-
trical characteristicsapply over an ambienttemperature range of 0' to +50° C, except as otherwise indicated.Warmup time
for given accuracy
is 20 minutes.
TABLE
2-1
ElectricalCharacteristics
Characteristic
h
'The fastest calibrated sweep rate is limited by some mainframes.
PerformanceRequirement
Sweep Rates
Calibrated Range
Variable Range
Sweep ~ccuracy'(With 7700, 7800, or 7900-Series
Mainframes)
Over Center 8 Div
5 s1Div to 1s1Div
0.5 s1Div to0.1 ps1Div
50 ns/Div to 10ns1Div
Excluded Portionsof Sweep
Start of Sweep
End of Sweep
Sweep Length (Unmagnified)
MAG Registration
PositionRange
POSITION Controls Fully Clockwise
POSITION Controls Fully Counterclockwise
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SWEEP GENERATOR
5 sldiv to 10nsldiv in27 steps. XI0Magnifier extends
fastest calibratedsweep rate to 1 nsldiv.
Continuously variable uncalibratedsweep rate toat least
2.5 timesthe calibratedsweep rate setting.
With SWP CAL adjusted at 1 msldiv within the temperature
range of +20° to+30° Ctoatiming referenceof 0.25%or
better.
+I 5' to+35' C
First 10ns in 7800, 7900-seriesmainframes.
First 20 ns in 7700-seriesmainframes.
First 50 ns in all other 7000-series mainframes.
Beyond 10thdiv unmagnified.
Beyond 100thdiv magnified.
At least 10.2 div at all sweep rates.
0.5 div or less from graticulecenter when changing from
MAG XI0toMAG XI.
Start of sweep must be tothe right of graticulecenter at
1msldiv.
End of sweep must be tothe left of graticulecenter at
1msldiv.
0" to +50° C
Unmag
4.0%
1.5%
2.5%
Unmag
5.0%
2.5%
3.5%
Ma9
5.0%
2.5%
4.0%
Ma9
6.0%
3.5%
5.0%