Gould 4070 User manual

(217) 352-9330 | [email protected] | artisantg.com

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Gould

4072/4074

Operators

Manual

•}

GOULD

Electronics

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Introduction

NOTE:

This

is

a combined

operating

manual

for

both

the

4072

2-Channcl

and

the 4074

4-Channel

Digital

Storage

Oscilloscope.

Throughout

the

operating

manual

the

following

convention

applies;-

4070

~

refers

to

both the 4072

and

4074.

4072-

refers

to

only

the

2

channel

4072.

4074-

refers to only the 4 channel 4074.

Gould's

4070 series of digital oscilloscopes have

hecn

designed

with

the

user

in

mind.

These

highly

sophisticated

instruments

are

particularly easy

to

usc.

To

obtain

a

trace

is especially

simple-

just

connect

the sig-

nal

and

press

the

Auto

Setup

button

the

4070

does

the

rest.

Having

obtained

a trace.

three

readily accessible cur-

sors

make

il

easy

to

take timing

and

voltage

measurements

directly

from

the

screen.

The

huilt~in

plotter

or

an

external

plotter

using

HPGL

can be used

to

make

a

hard

copy

of

the

display for

future

reference

a:-.

well.

For

the

more

advanced user.

the

4070

series

have

a

great

deal

to

offer.

The

GPIB(IEEE4SS)

and

RS423(RS-232)

interfaces a!lows control by a

computer,

hence

the

oscillo-

scope

can

be

left

unattended

whilst

it

continues

to

take

mea-

surements

and

plot

traces as

and

when

required.

All

of

tht.:

operating

functions

can be

controlled

by

the

computer

and

the

oscilloscope

can

output

complete

trace

data

to

the

com-

puter

for

further

analysis.

The

4070

incorporates

a

software

menu

system

allowing

functions to be easily accessed. For

example,

up

to

four

control

setups including

attenuator,

trigger,

GPJB

and

RS423 settings can

be

stored

in

battery-backed

memory

for

future usc with

the

'Save

and

Recall

Setups'

menu.

The

trigger menu allows

the

4070's triggering system

to

be

controlled

using a

'Trigger

Configuration

Diagram'.

This

is

designed

to

mimic

the

way

that

most

users

think

about

com-

plex triggering

requirements.

It

displays a flow

diagram

allowing various

conditional

triggering

options

to

be

set

and

combined

appropriately.

Options

include

event

counting,

time delays.

and

trace

B

to

wait for triggering

on

trace

A.

The

Display

menu

allows

control

of

some

of

the 4070's

most

advanced

facilities.

For

example,

using this

menu,

it

is

pos~

sihle to select the glitch

detection

function. This can be used

to

detect

transients

as

brief

as

5ns

even

on

the

slowest

timcbasc

ranges.

It

is

also

useful for alias

detection

in cer-

tain circumstances.

Another

option,

particularly useful

when

a trace has

been

magnified in the X direction, is inter-

polation.

The

4070 is

able

to

perform

rapid sine

interpola-

tion

on

captured

signals. Points

arc

calculated

and

inserted

between

the

actual

samples

which make up

the

originally

captured

trace.

The

original

trace

data is

not

lost

and

the

uninterpolated

display

can

he

retrieved at any time.

The

4070

can also

perform

linear

interpolation

if required.

The

oscilloscope

is

also fitted with a

keypad

interface,

allowing

Gould

waveform

processors

to

he

connected

to

provide

extra

functions.

These

include

automatic

measure-

ment

of

risetimc.

overshoot

and

frequency.

3

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Operation

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1.1.1

Power-on

Display

(4072)

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Focus

ll'umonat1on

Figure

1.1.2

Power-on

Display

(4074)

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.

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Section

1

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5

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1

Operation

Auto

Setup

0

wi!l

always

attempt

to

arrange

the

dis-

play

so

that

two to five

complete

cycles

appear,

with

the

amplitude

set

so

that

the

height

of

the

trace

is

roughly

two

to

five scn.:cn divisions.

It

also

selects

auto

trigger to

ensure

that the screen

is

frequently

updated

and a trace will be visible.

Adjusting

the

Trace

The

trace

can

he

altered

in

two

main

ways:

horizontally

and

vertically.

Basic

horizontal

adjustments

involve

altering

the

sweep

rate

of

the trace, so that the image

on

the screen

stretches

or

contracts

horizontally.

The

main

vertical

adjustment

is

the

height

of

the

displayed

signal-

i.e.

the

volts

per

screen division.

Horizontal

Adjustment

(A

TIME/DIV)

To

alter

the s\vccp rate of the trace. for

example

to

lnok

more

closely

at

part

of

the

image.

the

A TIME/DIV

paddle

is

used

(the

B TIME/DIV

paddle

i:--

discussed

in

Section

1

.3.).

With

the

4kHz

signal

applied

as

discussed

earlier.

Auto

Setup

may

have set

the

sweep

rate

to

50f1-S

per

screen

division

horizontally-

i.e.

each

horizontal

screen

division

represents

50/hs

worth

of

the

input

signal.

This

is

shovv·n

by

the

'TBA=50f.ts'

near

the

top

of

the

display.

The

·TBA'

means

that

the

A

timebase

is

in usc:

two

timcbases

arc

available

for

each

channel,

namely

A

and

B.

Usc

of

the

B

time

base

is

discussed in

Section

1.3.

A TIME/DIV ®

This

is

a five

position

paddle

which

con-

trols

the

sweep

rate

of

the

trace.

A

gentle

push

causes

a small

change

in

the

sweep

rate.

whilst a

firmer

push

will

cause

a large

change

in

the

sweep

rate.

Given

that

the

current

sweep

rate

is

50p,s

per

screen

divi-

sion,

a

single

push

and

release

of

the

paddle

to

the

right

will

change

the

'timebase'

from

50fl-S

per

division

to

20fl-S

per

division.

The

displayed

signa! will

stretch

accordingly.

A

second

single

push

to

the

right will

change

the

timehase

again,

this

time

to

10JLS.

If

you

keep

pushing

the

paddle

to

the

right.

you

will find

that

the

fastest

timebase

is

20ns

per

screen

division.

You

may

notice

that

at

l

00,50

and

20ns

per

division,

the

oscillos-

cope

builds

up

the

image

gradually.

This

is

because

it uses

a

method

called

'Equivalent

Time

Sampling'

or

ETS

for

the

faster

tirnebases.

It

takes

a

number

of

random

samples

of

the

signal

and

adds

them

to

the

display to

build

up

the

final

result.

This

is

only

useful

for

repetitive

input

signals.

If

you

now

push

the

paddle

to

the

left

you

will

sec

the

time

base

change

in

the

opposite

direction.

The

maximum

time

per

division

is

20s;

the

4070 will

take

over

3

minutes

to

acquire

a full

trace

at this

speed.

l·Iowever,

assuming

you

arc

applying

the

4kHz

signal

mentioned

earlier,

when

the

time

base

reaches

50ms,

an

'alias'

becomes

visible.

Section

1

Aliases

An

alias

is

a false

image.

The

4070

is

a digit

a!

oscilloscope

and

so

takes

frequent

samples

of

the

input

signal in

order

to

update

the

trace.

Thus

it may

take

one

sample

from

one

point

on

the

input

waveform

and

the next

sample

from a

point

slightly

further

along

on

the

next wave. It will

then

display

the

wave as

hcing

much

longer

than

it

really

is.

The

effect

is

similar in

principle

to

the

false

motion

of

wagon-

wheels

as

seen

on

a television.

The

4070

docs

however

have

a

feature

which will

often

help

you

to

spot

aliases.

If

the

input

signal

peaks

or

troughs

at

any

point

hctween

samples.

a

peak/trough

can

be

dis-

played.

This

Max-Min

function

is

discussed

further

in Sec-

tion

2.4.

Vertical

Adjustment

(VOLTS/DIV)

Each

of

the

channels

has

its

own

set

of

vertical

controls.

The

main

control

in

each

case

is

the

VOLTS/DIV (volts

per

divi-

sion)

paddle.

Again

this

is

a five-position switch. A

gentle

push

either

up

or

down

will result in a slow single

step

change

in

the

sensitivity

of

the

instrument.

A

firmer

push

will

cause

a

more

rapid

change.

VOLTS/DIV ®

This

is

a five-position

paddle.

It

adjusts

the

volts

per

division.

Pushing

the

paddle

upwards

will

adjust

the

sensitivity as

far

as SV/div

and

the

height

of

the

image

will

be

seen

to

decrease

in

accor-

dance

with

the

changes.

In

the

other

direction,

sen-

sitivity

can

be

increased

as far as

2mV

per

division,

increasing

the

height

of

the

screen

image.

Note: The 4070 can

accept

input

signals

with

a

peak

voltage

as

high

as

plus

or

minus

400V.

Larger

signals

can cause

damage

to

the

internal

circuitry.

AC/Gnd/Dc<i)

This

button

controls

the

type

of

coupling

between

the

input

signal

and

the

4070.

DC

is

the

most

generally

applicable,

and

auto

setup

will

normally

set

this

control

to

DC

where

possible.

However,

if

when

using

the

instrument

you

find

that

there

is a

permanent

vertical offset in

the

display-

i.e.

the

signal

is

consistently

displayed

too

high

or

too

low

on

the

screen

-you

could

try

pressing

this

button

once

to

set

it

to

AC.

This

will

cause

the

4070

to

remove

any

DC

compo-

nent

which

may

be

causing

the

offset.

Repeated

pressing

of

this

button

will

cause

it

to

cycle

through

the

three

settings

AC,

Ground

and

DC

With

this

control

set

to

DC,

the

4070

can

display signals in

a

frequency

range

of

OHz(DC)

to lOOMHz. On

AC,

the

range

is 10Hz

to

IOOMHz~

With

the

setting

on

Gnd

(ground)

a

OV

reference

only

is

displayed

(the

input

signal

is

not

connected

to

ground

or

coupled

to

the

trace

in this

case).

This

control

is

discussed

in

more

detail

in

Section

1.2.

7

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1

?.

Operation

Section

1

sample

actual

signal

«0\

/(\

\ I \ \j \

/

/\

I \

I

f\

v v

illusory

image

Figure 1.1.6

Alias

Generation

Operating

Hints

The

following list gives some

of

the

more

commonly

met

problems in

operating

digital oscilloscopes, how

to

correct

them,

and

a

brief

explanation

of

what was wrong.

You may

need

to

consult later sections of

the

manual

as not

all the

operating

features have

been

discussed so far.

Problem:

No

trace

visible.

Trace

intensity

too

low

~

Correct

with

Trace

Intensity

Control.

Turn

on

other

trace.

No

stable

trigger -Select

Auto

Trigger

until

Too

much

vertical shift

trace found.

-

correct

with the vertical

Position

paddle.

Too

much

post storage shift- cancel post

storage

shift.

Input

has

large

DC

offset -

AC

couple

input

signal.

-

correct

with

position

paddle.

-use a less sensitive range.

Problem:

Trace

not

heing acquired.

Trigger

level incorrect

Trigger

source

on

the

wrong

input

Trigger

coupling on an

unsuitable setting

Hold

on

Timebase

on very slow

acquisition

-select

AUTO

and

DC

trigger,

then adjust

the

level control

until

the

trigger level

'bars'

are

lined

up

with

the

centre

of

the

trace.

-

change

trigger

source.

-

change

trigger coupling.

-release Hold.

-

adjust

timebase

speed.

Insufficient signal to

trigger on

Instrument

in

single

capture

mode

-use

Auto

Trigger.

-press Continuous.

Problem:

·rrace

is

unstable even when triggered.

Alias

Noisy

input

Trigger

on

AUTO

Input non-repetitive

Input

has many

non-

identical trigger points

-check for alias with max-min

glitch detect and select a

faster tirnebase range.

-select

DCLP

or

ACLP

trigger

coupling.

-select bandwidth limit.

-adjust trigger level.

-With low frequency inputs,

below 40Hz,

AUTO

trigger

will not work correctly.

Select Normal trigger.

-Select

NORM

trigger

mode

and S/ShoL

-use divide by N.

Problem: Trace has a very flat

top

or

bottom.

Trace

captured

when

in

limit

and

post storage

shift has been used.

-adjust

pre-storage shift.

-use

tess sensitive range.

Problem: Trace

is

very

'dotty'.

Too

much horizontal

expanswn

-decrease

expansion.

-use linear or sine

interpolation.

-re-capture on a faster

timebase range.

9

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1

Operation

shown in front

of

the

attenuator

setting

when

variable

is

used.

Also.

when switching

between

Cal

and

Uncal

the var-

iable

setting

is

memorised

so

that

the

'Uncal'

ratio

can be

recalled.

Example

screen display:

Channel

1

is

set

to

a sensitivity

of

5 volts per

screen division.

C2>20m

V

Channel2

is

uncalihrated

and

the

attenuator

is

set to a reduced sensitivity. (i.e.

greater

than

20mV

per

screen division.)

The

status

of

the Step/Var

button

is

indicated

by the illumi-

nated

letters

above the

button.

Depending

upon

this,

the

VOLTS/DIV paddle will

operate

as

follows:

Cal

When

Cal

is

illuminated the

paddle

steps

the

attcnuator

through the discrete

calibrated

ranges

from

2mV

to

SV

per

screen

division in 1, 2, 5 steps.

With a

xlO

probe the ranges arc 20mV to 50V per

division at the probe input.

Uncal

The

coarse setting

of

the

attenuator

remains

unchanged,

but a variable gain

is

applied to the input

signa!. This gain has a range

of

l

to

about

0.4.

Thus.

with an initial setting

of

l

V,

the actual sensitivity of

the channel could be set

by

the

paddle

to anywhere

between

1V and 2.5V

per

division.

Note:

If

the

Gould

?836

x10

probe

is used,

it

will

be

detected

and

the

correct

sensitivity

will

be

displayed.

Position

®

The

Position paddle controls the vertical position

of

the

trace(s) for its channeL

It

has

the

following settings: Fast

up,

slow

up.

no

shift, slow down

and

fast down.

If

either

of

the

A

orB

Post

Storage

lights

are

lit, then the

Position

paddle

will apply

'post~storage

shift' to the relevant

trace(s).

The

paddle will move the trace in the

same

way

as

before.

When

the light

Is

off, the trace will

return

to its orig-

inal vertical position. This shifted position

is

memorised

and

can he recalled later by switching the light on again.

When

post~storagc

shift

is

used.

any

part

of

the trace which

would have

been

off~screen

at

the

ADC

limits will be

replaced by a horizontal line.

Post

Storage

(j)

The

three

PostStorage buttons. Hold, A

and

B,

arc

used for

freezing a trace and determining which

traces

may he

affected by the Position paddle:

Hold

Freezes

the trace on the screen the

moment

it

is

pres~

sed. In dual timcbase

mode,

both

traces

will be held.

It

is

not

possible to have

one

timcbase held whilst

keeping

the

other

one live.

A

B

Section

1

Pressing this

button

switches the A light on and off.

When the A light

is

illuminated, the Position

paddle

will add post-storage shift

to

the A trace.

Pressing this

button

switches the B light on and off.

When the B light

is

illuminated. the Position

paddle

will add

post~storagc

shift to the B trace.

Note:

Post-storage

shift

is

only

available

on

live traces

when

in

dual

timebase

mode,

when

it

is

useful

for

pro-

ducing

trace

separation.

Post-storage

shift

may

be

added

to

traces

in

single

timebase modes,

but

only

when

held.

Cursors@

The

cursors may be called

onto

any channel

by

pressing the

respective

channel's

Cursor

button.

If

only one timcbase

is

in

usc then the cursors will go

onto

the only displayed trace.

In

dual timebase

mode.

the cursors

will

initially

appear

on

trace

A:

a second press

of

the button will transfer them to

the B trace. A

third

press of the button switches the cursors

off.

For

a full description

of

cursor

operation.

sec Section 1.6.

1.3 HORIZONTAL POSITION AND TIMEBASE

The

controls discussed in this section allow the trace to be

moved sidew;Jys. magnified (i.e. stretched). and observed

at widely varying sweep rates, allowing signals

of

greatly

differing characteristics to be examined with equal ease.

Timebase

Settings

G)

The

two timebases which

arc

available for the input signal

arc set by the A

and

B

'TIME/DIV'

paddles. As with all the

paddles. these

arc

five position switches; they control the

rate at which the timebase

is

changed.

Moving

either

of

the

paddles to the left reduces the sweep

speed (acquisition

rate)

forth

at trace.

When

20

seconds

per

division

is

reached,

further

leftward presses will be ignored.

Moving the

paddle

to

the right increases the sweep speed,

up to

:1

maximum

of

20ns/div (sec

'Equivalent

Time

Sampl-

ing' below).

The

paddles

change the timebasc in 1, 2, 5

steps.

One

of

the special features

of

this oscilloscope

is

its ability

to display the

input

signals alternately on two

independent

tirnebases.

For

example,

it

is

permissible to display the A

trace with its time

base

set to lms/div and then display the B

trace with its timebase

set

to 20,us/div. Visually of course,

the alternation

is

so fast that no flickering

is

visible.

Note: The fastest

non~ETS

(see

below)

capture

rate is

250ns

per

division.

There is no

200nsldiv

range.

Equivalent

Time

Sampling

The

three

fastest timebase ranges, 100, 50 and 20ns/divi-

sion,

arc

produced by Equivalent Time Sampling,

or

ETS.

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Operation

Trace

Position

®

The

Position

paddle

Is

used to

move

the

trace

to

the

right

and

left.

The

paddle

has five

settings:

fast

righL

slow

right;

no

shift; slow left;

and

fast left. In

addition,

after

a few

moments

on

the

fast settings

the

rate

of

shift

accelerates.

The

position

of the

cursors

(sec

Section

I.6

for

more

about

these)

is

fixed in relation

to

the

trace

and

they

will

move

with

the

applied

shift.

With

X

magnified

traces,

the

cursors

can

he

off-screen.

To

bring

them

back

into

view

it

is

neces-

sary to usc the CURSOR position paddles.

1.4 BASIC TRIGGER CONTROL

The

trigger

facilities

offered

by

the

4070

are

very

com-

prehensive;

those

discussed

here

arc

controllable

directly

from

the

front

panel.

For

the

more

advanced

menu-control-

led facilities.

sec

Section 1.3.

The

default

setting

of the

instrument

on

first

power-up

is

as

follows:

The

A trigger will

be

set

to

initiate

captures

on

the

A

time

base

range

and

the

B

trigger

will

he

set

to

initiate

captures

on

the

B time

base

range.

lf

no

buttons

arc

pressed

within 30

seconds

of

power

down,

then

the

power

down trigger

setting

will be

retained

on

future

power-up.

G)_

..________AlB

TRIGGER

I

.-~,~_~,~~------~,=~,~,~--

Status I t I I I L

A

,~,L-----------------

Figure

1A. 1

Trigger

Controls

(Both

4072

and

4074)

Section

1

Selecting

Source

and

Coupling

The

two

trigger

channels

A

and

B may

be

set

independently

to

any

of

the

allowable

combinations

of

source

and

coup!~

ing.

When

EXT,

external

input.

is

selected

as

the

trigger

source,

A

takes

its

input

from

the

EXTERNAL

TRIGGER

A

BNC

socket,

and

B

take:::.

its input from

the

EXTERNAL

TRIGGER

B

BNC

socket.

A/8

TRIGGER @

This

button

controls

which

channel's

status

is

viewed

on

the

Ll-::D

display.

The

light

above

the

button

shows

which

channel

is

currently

being

displayed.

When

selected

in this way

the

source

and

coupling

buttons

\Vill

change

the

setup

of

the

ch;mncl.

Source

@steps

through

the

available

options

of

trigger

source.

After

line

ha:::.

been

selected.

a

further

press

of

the

button

returns

the

selection

to

CH

1

The

options

arc:-

4072-

CHI,

CH2,

FXT

and

LJNL

4074

-CHI_

CH3,

EXT and

LINE.

Coupling @

Steps

through

the

available

options

of

trigger

coupling.

These

arc

AC.

ACHP(AC

High

Pass),

ACLP(AC

Low Pass),DC, &

DCLP(DC

Low

Pass).

After

DCLP

has

been

selected,

a

further

press

of

the

button

return:::. the selection

to

AC.

All

the

cou-

plings

can

be

used with

the

internal

and

EXT

sources.

For

LINE,

the

input

coupling

is

not

selectable.

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Operation

Trigger

Delay

Thi.:.-

option

allows the user to set two types

of

delay: delay

by

time

and

delay by events.

The

initiation

of

a

capture

will

not

then

take

place until

the

delay

conditions,

as

described

below. have

been

met.

The

two types

of

delay

arc com-

pletely

independent

and

it

is

possible

to

combine

the two. A

trigger

event

as discussed belov.'

is

a valid

trigger

as set by

the

Source,

Coupling,

TRIG

LEVEL

and

Slope controls.

Delay

by

Time

@)

This

is set by the Time

TRIGGER

DELAY

paddle.

This

has five settings: decrease time fast,

decrease

time

slow. no

change,

increase

time slow

and

increase

time

fast.

The

delay time

step

size

is

dependent

on

the

chosen

timebase

setting.

Time

A

gentle

push to the left

decreases

the

time

delay: a

firmer

push

causes

the

delay to

decrease

at

a faster

rate.

A gentle push to

the

right

increases

the time

delay; a firmer press increases

it

at a

faster

rate.

If

the

delay

changes to

zero,

there

will be a

pause

before

the

change

continues.

If

the

time delay

is

zero,

lhe trigger

point

will he at the

ldt~

band

edge

of

the

screen.

When

the

delay increases from

zero,

the

display shows events

after

the

trigger

point;

i.e.

the

trigger

point

moves

to

the

left

and

disappears

from the

screen

altogether.

The

maximum

delay

is

dependent

upon

setting.

Time

base

Range

20s/div

to

0.1

ms/div

50,us/div to 50ns/div

20ns

Maximum

Delay

99.9s

0.99s

0.4s

The

current

trigger delay setting

is

shown in

the

screen

tt:xL

e.g.

TBA

~

1

011/Ls

Trig

Dly

~

3110.0/Ls

The

A

time

base

is

set to 100 microseconds

per

division and

there

is

a delay

of

300 microseconds from

the

trigger point

to

the

start

of

acquisition. i.e. 3

screen

divisions.

When

the

time

delay

is

decreased

from

zero.

the display

shows

events

leading up

to

the trigger

point:

i.e.

the

trigger

point

moves

to

the right

and

pre-trigger

events

arc

cap-

tured.

The

maximum

amount

of

pre-trigger

or

negative

delay

time

that

can

he

captured

is

1whole

screen.

When

this

is

reached,

the

trigger point

is

on

the

right-hand

edge

of

the

screen.

Negative

delay

time

is

displayed

on

the

screen

as a percen-

tage

of

pre-trigger,

e.g.

TBA

=

.'iO,us

Pre

Trig

=

30.2%

The

A

timebase

is

set to 50 microseconds

per

division and

there

is

-150.5microscconds

delay. In

other

words,

the trig-

ger

point

is

just

over

three

divisions from

the

left-hand

side

of

the

screen.

Section

1

Delay

by

Events

®

NOTE:

This

function

is

available when

either

A divided by

N

orB

delayed

by

N

is

selected from

the

trigger

menu

(sec

section 23.

This

option

allows

the

user

to

control

the

number

of

trigger

events

to be

detected

before

a trace

is

to

be

acquired.

'T'he

delay

is

set by

the

Events

TRIGGER

DELAY

paddle.

This

too

has five settings: fast decrease; slow decrease; no

change;

slow

increase

and

fast increase.

Events A

gentle

push

to

the

left

decreases

the

number

of

events,

a firmer

push

decreases

the

number

of

events

at

a faster

rate.

A

gentle

push to

the

right increases

the

number

of

events,

a firmer

push

increases

the

number

more

quickly.

The

number

of

events

currently

selected

is

shown

on

the

screen;

e.g.

Events=

3

The

A time

base

is set

to

100 microseconds

per

division

and

the

displayed trace was

captured

after

three

valid

trigger

events

were

detected.

The

minimum

number

of

events

delay

is

zero,

whereby

the

trace

will be

captured

following

the

first trigger event.

The

maximum

number

of

events

by which

capture

can

be

delayed

is

999999 (sec

Section

2.3).

Note

that

A

~

N

and

B delayed by N

cannot

be

selected

together.

1.5 BASIC CAPTURE FACILITIES

The

basic

capture

facilities

on

the

4070 allow the user to

freeze the trace

on

the

display.

There

are

two ways

to

do

this: a single-shot

capture

whereby

a full screen

is

acquired

then

frozen.

or

by pressing a Hold

button.

Using a Hold

but-

ton

freezes

the

display

the

moment

it is pressed; this can

cause

a

discontinuity

in

the

trace as

the

displayed waveform

may

contain

data

from

more

than

one

capture.

S/Shot

®

This

button

arms

the

instrument

for a single··

shot

capture.

The

Arm'd

light will

be

illuminated

to

show

that

the

button

has

been

pressed.

Arm'd

@)

This

light illuminates after

the

S/Shot

button

has

been

pressed;

it will stay lit until

either

a valid

trigger has

hcen

received

or

until

the

Continuous

but-

ton is

pressed.

Stor'd

@

This

light illuminates on completion

of

a

single-shot acquisition. This

is

after

the

instrument

bas

been

Arm'd,

triggered

and

a trace acquired.

The

light will

stay

illuminated

until the

instrument

is

re-

armed

or

Continuous

is pressed.

Continuous

®

This

button

puts

the 4070

in

continuous

capture

mode

(i.e. its default

state).

The

instrument

will

automatically

re-arm itself

after

each

capture

is

completed;

this

enables

the displayed traces

to

be

updated

as

frequently

as possible.

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Operation

On

the

4070 there arc three

buttons

lahcl!cd

'Hold'.

One

is

located in a

group

including

buttons

S/Shot

and

Continuous:

Hold

G)

Freezes the displayed traces

immediately

irrcs··

pcctivc

of

the stage any

ongoing

acquisition

m:1y

have

reached.

The

Hold lights

of

the respective channels

will be illuminated.

To

release hold simply press the

Hold

button

again.

The

other

two

'Hold'

buttons

arc

associated

\vith the

two vertical channels; they can be

found

next to the

Position paddles. (Sec Section 1.2).

Hold

These

buttons freeze

the

traces

of

the

selected

chan-

nel only.

The

Hold light will

be

illuminated.

To

release the channel

hold

simply press

the

channel

Hold

button

again. (Sec also Sections 1.2 and 1.3).

1.6 CURSOR MEASUREMENTS

The

4070 allows you to take direct

measurements

from the

screen display automatically. using inbuilt cursors. These

arc

movable

reference lines which the oscil!oscopc can dis-

play. It takes

the

measurements

between

these

lines.

Cursor Selection

G)

The

cursors

for each channel

arc

switched

on

or

off using

the

Cursor

button

for the respective

channel.

If

the

cursors

are

on.

this will he indicated by a light

above

the

button.

If

X magnification (sec Section 1.3)

is

in

usc,

the

cursors

may

not

be

visible

on

the screen, but this

is

easily

remedied

using

the

paddles

described below.

The

cursors can be used on

either

the

A

or

B traces,

selected

by

successive presses

of

the

button,

assuming both traces arc active.

Cursor

One

press

of

this

button

brings

the

cursors

on

the A

timebase trace.

Another

press

moves

them

to

the

B

timebase trace. A third press

of

the

button

switches

the

cursors off.

If

only

one

timcbase

is

displayed, the

cursors

will

be called

up

onto

that

trace;

a

further

press

of

the

button

will de-select

the

cursors.

The Cursors

Once

activated by a press

of

the

Cursor

hutton,

three

cur-

sors will

appear,

as indicated in Figure 1.6.2.

The

large

dashed

vertical line

is

the

'time

datum'

cursor

and

the short

vertical line is the

'minor'

cursor.

The

dashed

horizontal

line

is

known

as the 'voltage

datum'

cursor.

Note

that

if the

cursors

are

already selected for

one

channel,

selection

of

cursors for

the

other

channel will

automatically

swap

them

over

to

the

new channel.

Movement

of

the

cursors

!S

achieved

using the DATUM

and

ClJRSOR

paddles.

Movement@

The

three

cursor

movement

paddles

are

each

five-position

switches.

'T'he

left-hand DATlJM 3

paddle

moves

the

vol-

tage

datum

cursor

vertically. and the

right-hand

DATlJM

paddle

moves

the

'time

datum'

cursor

horizontally.

The

Cursor

paddle

moves the

minor

cursor

along

the

trace-

i.e.

Section

1

the

minor

cursor,

when moved horizontally, automatically

follows the trace. up and down as welL

Making

Measurements

Exampll!: Frequency

and

Peak

ro

Peak Volragc.

In Figure 1.6.2,

the

time and voltage

datum

cursors have

been

positioned using the DATlJM paddles so that

they

cross at the

trough

of

the

waveform.

The

minor

cursor

has

been

positioned

at

the

peak

of

the waveform using the

Cur~

sor

paddle.

The

voltage

is

given at the

bottom

of the display

in

the

form

'TRIA:

5.25V'.

In

other

words.

the

vertical dif-

ference

between

the

point

where the minor

cursor

in

terse~

cts

the

trace

and

the

voltage

datum

cursor

is

5.

25

Volts.

The

'TRIA'

tells you

that

the

measurement was

obtained

from

channcll

trace

A.

At

the

bottom

right

of

the

screen

is

the reading '551.0

fJ-S',

i.e. the time diffcn:ncc between the minor cursor and

the

time

datum

cursor

is

551

microseconds. This reading

is

for

half a cycle. so

the

reading

for a

fu!l

cycle should be

1102

microseconds.

The

frequency

is

therefore

1/ll.OOJ

!02 =

tJ07Hz.

Greater

accuracy could he

obtained

by moving

the

minor

cursor

to

the

next trough (where

the

voltage differ-

ence

is

zero)

and

finding

the

frequency for a

complete

cycle.

In

general,

greatest

accuracy

is

obtained by taking

measure-

ments

where

the

slope

of

the waveform

is

at its

steepest.

suchas at 0

Volts

rather

than

at -2.125V as

in

this cxmnplc.

E:xample: Rise Time

The

rise time

of

a wave

is

the time

it

takes

to

traverse

the

central

HO'X1

of

its vertical movement.

To

measure

the

rise

time of, say, a simple sine wave such as

that

shown

in

Figure

1.6.3, you would first

of

all measure the

peak

to

peak

vol-

tage as shown in

the

previous example.

Suppose

the

result

of

this

measurement

is 5.25V. Now you would move tbc

time

datum

cursor

to

the

right using the right-hand

DATlJM

paddle

until it

is

at

a

point

10%

of

the way up the waveform.

Also, usc

the

left-hand DATUM

paddle

to

move

the

voltage

datum

cursor

up so

that

it intersects

the

time

datum

cursor

at

the

point

where it crosses

the

trace. This

would

be

where

the

vertical difference

between

the

voltage

datum

cursor

and the

mmor

cursor

was 5.25-

0.525~4.

725V.

You

would

then

move

the

CURSOR

paddle

so

that

the

vertical

difference

reduces to 4.725-0.525

=4.2V.

The

reading in

the

lower right-hand

corner

of

the

screen

would then

be

the

rise time.

1.71NPUT/OUTPUT

The

4070 is

equipped

with RS423 and

GPJB(IEEE488)

interfaces, allowing

communication

with a

host

computer.

Tn

addition,

there

is also a keypad option

and

a Miscellane-

ous

I/0

connector,

which among

other

things is used for

the

analog plot

outputs.

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Gould 4070 User manual

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