Tektronix 7b50a User manual

7B5DA

TIME

BASE

WITH

O

PTIONS

Scans

By

Arlel.Media

Artek Media

1042

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mme

r

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WARRANTY

All

TEKTRONIX instruments are warranted against

defective materials

and

workmanship

for

one year.

Any

questions

with

respect to the warranty should

betaken

up

with

yourTEKTRONIX

FieldEngineer

or

representative~

All

requests

for

repairs

and

replacement parts

should

be

directed

to

;'1\e

TEKTRONIX Field

Office

or

representative in

your

area.

This

will

assure

you

the fastest possible service. Please

include

the

instrument

Type

Number

or

Part Number

and

Serial

Number

with

all requests

for

parts

or

service.

Specificationsand pricechangeprivilegesreserved.

Copyright

(C)

1975 by Tektronix, Inc., Beaverton,

Oregon. Printed in the United States

of

America.

All

rights reserved. Contents

of

this

publication

may

not

be reproduced in any

form

without

permission

of

Tektronix, Inc.

U.S.A.

and

foreign TEKTRONIX

products

covered

by

U.S.andforeign patents

and/or

patentspending.

TEKTRONIX is a registered trademark

of

Tektronix,

Inc.

7B50A

Instruction

TABLE

OF

CONTENTS

PAGE PAGE

LIST OF

ILLUSTRATIONS

...................

iii

Trigger Slope

....................

1-7

LIST OF

TABLES

..........................

iv Trigger Level . . . . . . . . . . . . . . . . . .

..

1-7

SAFETY

SUMMARY

.........................

v Horizontal

Sweep

Rates

.............

1-7

SECTION 1 OPERATING INSTRUCTIONS Time Measurement

................

1-7

@

INSTALLATION

...................

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

Sweep Magnification

...............

1-7

Variable Hold

Off

.................

1-7

Mainframe Operating Modes . . . . . . . . . . 1-9

APPLICATIONS

........................

1-10

TIME-INTERVAL

MEASUREMENTS

.....

1-10

Period

and

Frequency Measurements

.....

1-10

Rise-Time

and

Fall-Time Measurements

...

1-11

Pulse

Width Measurements

...........

1-12

DELAYED-SWEEP MEASUREMENTS

.....

1-12

X-Y PHASE MEASUREMENTS

..........

1-12

Trigger Coupling

..................

1-6 SECTION 2 SPECIFICATION

Trigger Source . . . . . . . . . . . . . . . . . . . 1-6

STANDARD

ACCESSORIES

...........

2-3

WARNING

THE

REMAINING

SECTIONS OF

THIS

MANUAL

CONTAIN

SER-

VICING

INSTRUCTIONS. THESE

SERVICING

INSTRUCTIONS

ARE

FOR

USE

BY

QUALIFIED

PERSONNEL

ONLY.

TO

AVOID

ELECTRICAL

SHOCK, DO

NOT

PERFORM

ANY

SERVICING

OTHER

THAN

THAT

CALLED

OUT

IN

THE

OPERATING IN-

STRUCTIONS UNLESS

QUALIFIED

TO DO

SO.

----------------------------------~~-----

----~-

7B50A

Instruction

TABLE

OF

CONTENTS

(CONT.)

PAGE

SECTION 3

THEORY

OF

OPERATION

BLOCK

DIAGRAM

DESCRIPTION

...........

3-1

DETAILED

CIRCUIT

DESCRIPTION

.........

3-1

LOGIC

FUNDAMENTALS

.............

3-1

NON-DIGITAL

DEVICES

..............

3-2

FRONT-PANEL

DISTRIBUTION

~>

....

3-7

TRIGGER

GENERATOR

0 .......... 3-7

LOGIC 0 ...................... 3-9

SWEEP

GENERATOR

0 ............3-11

TIME/DIVISION

READOUT

~

........

3-14

INTERFACE

CONNECTORS

AND

POWER SUPPLY

<§>

...............3-14

SECTION 4

MAINTENANCE

PREVENTIVE

MAINTENANCE

.............

4-1

CLEANING

.......................

4-1

VISUAL

INSPECTION

................

4-1

LUBRICATION

....................

4-1

SEMICONDUCTOR CHECKS

...........

4-2

ADJUSTMENT

AFTER

REPAIR

..•......

4-2

TROUBLESHOOTING

....................

4-3

TROUBLESHOOTING

AIDS

...........

4-3

TROUBLESHOOTING

EQUIPMENT

......

4-5

TROUBLESHOOTING

TECHNIQUES

.....

4-6

CORRECTIVE

MAINTENANCE

.............

4-9

OBTAINING

REPLACEMENT

PARTS

.....

4-9

ii

PAGE

SOLDERING

TECHNIQUES

............

4-9

COMPONENT

REMOVAL

AND

REPLACEMENT

...................

.4-10

Circuit

Boards

...................

.4-10

Switches

......................

.4-12

Semiconductors

.................

.4-12

Interconnecting

Pins

..............

.4-13

Front-Panel

Lights

................

.4-16

ADJUSTMENT

AFTER

REPAIR

..

,

.....

.4-16

INSTRUMENT

REPACKAGING

........

.4-16

SECTION 5

PERFORMANCE

CHECK

AND

ADJUSTMENT

PRELIMINARY

INFORMATION

........

5-1

TEST

EQUIPMENT

REQUIRED

.........

5-1

INDEX

TO PERFORMANCE CHECK

AND

ADJUSTMENT

PROCEDURE

.......

5-3

PRELIMINARY

PROCEDURE

..........

5-3

SECTION 6

REPLACEABLE

ELECTRICAL

PARTS

SECTION 7

INSTRUMENT

OPTIONS

SECTION 8

DIAGRAMS

AND

CIRCUIT

BOARD

ILLUSTRATIONS

SECTION 9

REPLACEABLE

MECHANICAL

PARTS

CHANGE

INFORMATION

@

--~---

FIGURE

NO.

@

1-1

1-2

1-3

1-4

1-5

1-6

1-7

1-8

2·1

3-1

3-2

3-3

3-4

3-5

3-6

4-1

4-2

4-3

4-4

7B50A

Instruction

LIST

OF

ILLUSTRATIONS

PAGE

Frontispiece

......................

vi

Location

of

release

latch.

. . . . . . .

1-1

Front-panel

controls,

connectors,

and

indicators.

. . . . . . . . . . . . . . 1-2

Effect

of

LEVEL

control

and SLOPE

switch

on

crt

display . . . . . . . . . . . 1-8

Area

of

graticule

used

for

most accurate

time

measurements . . . . . . . . . . . . . . . . 1-9

Operation

of

sweep magnifier . . . . . . 1-9

Measuring the period and

determining

the

frequency

of

a displayed waveform

...

1-10

Measuring the rise

time

and fall

time

of

a displayed waveform

...............

1-11

Measuring the pulse

width

of

a displayed

waveform

.......................

1-12

7B50A

dimensional

drawing.

. . . . . 2-3

Basic

block

diagram

of

the

7B50A

Time-Base

Unit.

. . . . . . . . . . . . . . 3-2

Detailed

block

diagram

of

Trigger

Generator . . . . . . . . . . . . . . . . . . . 3-6

Functional

diagram

of

Trigger Source

Selector. . . . . . . . . . . . . . . . . . . . . 3-8

Timing

diagram

for

Gate Generator

(092,

096,

098).

. . . . . . . . . . . . . . 3-9

Detailed

block

diagram

of

Logic

circuit

...

3-10

Detailed

block

diagram

of

Sweep

Generator . . . . . . . . . . . . . . . . . .3-12

Lubrication

procedure

for

a

typical

cam

switch.

. . . . . . . . . . . . . . . 4-2

Semiconductor

lead

configuration

.....

. 4-4

Inter-board

multi-pin

connector

assembly

..............

. 4-5

End-lead

multi-pin

connector

assembly

......................

. 4-5

FIGURE

NO.

4-5

Location

of

pin numbers

on

Interface

PAGE

connector

. . . . . . . . . . . . . . . . . . . . . . 4-5

4-6

7B50A

troubleshooting

chart. . . . . . . 4-8

4-7 Readout board removal procedure

.....

.4-11

4-8

Coaxial end-lead connector assembly

....

.4-12

4-9 Cam switch removal procedure

........

.4-14

4-10

4-11

4-12

Removal procedure

for

typical

push-button

switch

...........

.

Exploded view

of

circuit-board

and ferrule

................

.

Front-panel

light

socket assembly

..

.4-15

.4-16

The

illustrations

in Section 8 are located near

their

associat-

ed

Diagrams on

the

foldout

pages.

8-1

Semiconductor

lead configurations.

8-2

Location

of

circuit

boards in the

7B50A.

8-3 A

1-lnterface

circuit

board assembly.

8-4

A2-

Trigger

circuit

board assembly.

8-5

A3-Readout

circuit

board assembly.

8-6 A

1-lnterface

circuit

board assembly.

8-7

A2-

Trigger

circuit

board assembly.

8-8 A

1-1

nterface

circuit

board assembly.

8-9 A

1-1

nterface

circuit

board assembly.

8-10

A3--Readout

circuit

board assembly.

8-11

A1-lnterface

circuit

board assembly.

8-12

A3-Readout

circuit

board assembly.

8-13 A

1-1

nterface

circuit

board assembly.

8-14

A5-X-Y

Switch

circuit

board assembly.

8-15

Location

of

Sweep

Timing

adjustments.

8-16

Location

of

Triggering adjustments.

iii

7B50A

Instruction

LIST

OF

TABLES

TABLE

NO.

2-1

2-2

2-3

3-1

iv

PAGE

Electrical Characteristics

.............

2-1

Environmental Characteristics

.........

2-3

Physical Characteristics

..............

2-3

Basic Logic Reference

..............

3-3

TABLE

NO.

3-2

5-1

5-2

5-3

PAGE

Readout

Character

Selection

..........

3-15

Test

Equipment

..................

5-2

Sweep

Timing

....................

5-10

Magnified

Sweep

Timing

.............

5-10

@

r----

7B50A

Instruction

SAFETY

SUMMARY

This

manual

contains

safety

information

which

the

user

must

follow

to

ensure

safe

operation

of

this

instrument.

WARN ING

information

is

intended

to

protect

the

operator;

CAUTION

information

is

intended

to

protect

the

instrument.

The

following

are

general

safety

precautions

that

must

be

observed

during

all phases

of

operation

and

maintenance.

[WARNIN<!:I

Ground the Instrument

To

reduce electrical-shock hazard, the mainframe (oscilloscope) chassis

must

be

properly grounded.

Refer

to the mainframe

manual for grounding information.

Do

Not

Operate

in

Explosive Atmosphere

Do

not

operate this instrument in an

area

where flammable gases

or

fumes

are

present. Such operation could cause

an

explosion.

Avoid Live Circuits

Electrical-shock hazards are present in this instrument. The protective instrument covers

must

not

be

removed

by

operating

personnel.

Component

replacement and internal adjustments

must

be

referred to qualified service personnel.

Do

Not

Service or Adjust Alone

Do

not

service

or

make

internal adjustments to this instrument unless anotherperson, capable

of

giving first aid and resusci-

tation,

is

present.

Warning Statements

Warning

statements

accompany

potentially

dangerous

procedures

in

this

manual.

The

following

warnings

appear

in

this

manual

and

are listed

here

for

additional

emphasis.

To

avoid electrical shock, disconnect the instrument from the

power

source before soldering.

To

avoid electrical shock, disconnect the instrument from the

power

source before replacing components.

Handle silicone grease with

care.

A void getting silicone grease in eyes.

Wash

hands thoroughly after use.

@ v

7850A

Instruction

_.

TRIGGERING

~£VH

e

;r-'~

-

...

,

..

,.OSITIO.

• •

all'

II

•••

~,

II

\:i

--

.I

,

-

W

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EXT

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~

,..

TIME

BASE

7B50A

__

~..:...;,...;.._~

7B50A FEATURES

The 7B50A Time-Base

unit

provides calibrated sweep rates from 5 seconds to

50

nanoseconds and triggering

to

150

mega-

hertz for 700Q-series oscilloscopes. A

Xl0

Magnifier increases each sweep rate by a factor

of

10 and a VAR IABLE TIME/

DIV

control provides continuously variable sweep rates between calibrated steps. Variable hold

off

and alphanumeric readout are

provided. Also. when operating

in

the AUTO

TA

IGGER

ING

MODE, a bright baseline trace

is

displayed

in

the absence of a

trigger signal. The

7850A

can' be operated

as

an independent time base or

as

a delayed-sweep unit with a companion delay-

ing

time-base unit, Sweep mode

is

determined by the companion delaying time base.

1985-2

,;

"

--.,

-

Section

1-7B50A

OPERATING

INSTRUCTIONS

The

lB50A

Time-Base

unit

operates

with

a

Tektronix

lOOO-series

oscilloscope

mainframe

and

a

lA-series

amplifier

unit

to

form

a

complete

oscilloscope

system.

This

section

describes

the

operation

of

the

front-panel

controls

and

connectors,

pro-

vides general

operating

information,

a

functional

check

procedure,

and

basic

applications

for

this

instrument.

INSTALLATION

The

time-base

unit

is

designed

to

operate

in

the

horizontal

plug-in

compartment

of

the

mainframe.

This

instrument

can

also be installed

in

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

in

Section

2.

2. Install

an

amplifier

plug-in

unit

in a vertical

compart-

ment.

3.

Set

the

time-base

unit

controls

as follows:

(+)

Pop

AUTO

AC

INT

Midrange

1 ms

To

install

the

unit

in a plug-in

compartment,

push

it in until

it fits

firmly

into

the

compartment.

The

front

panel

of

the

unit

should

be flush

with

the

front

panel

of

the

mainframe.

Even

though

the

gain

of

the

mainframe

is

standardized,

the

sweep

calibration

of

the

unit

should

be

checked

when

in-

stalled.

The

procedure

for

checking

the

unit

is

given

under

Sweep

Functions

in

the

Functional

Check

procedure

in

this

section.

SLOPE

MODE

COUPLING

SOURCE

POSITION

TIME/DIV

VARIABLE

Calibrated

(Pushed in)

To

remove

the

unit,

pull

the

release latch (see Figure 1-1)

to

disengage

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 1-2

shows

and

provides

a

brief

description

of

all

front-panel

controls,

connectors,

and

indicators.

More

detailed

information

is

given

in

the

General

Operating

Instructions.

FUNCTIONAL

CHECK

The

following

procedures

are

provided

for

checking

basic

instrument

functions.

Refer

to

the

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

to

the

instruction

manual

for

maintenance

and

adjust-

ment

procedures.

Setup

Procedure

1.

Install

the

time-base

unit

being

checked

in

the

A hori-

zontal

compartment

of

the

mainframe.

@

(CAL IN)

HOLD

OFF

MAG

MIN (fully

counter-

clockwise)

X1

(pushed

in)

4.

Turn

on

the

mainframe

and

allow

at

least

20

minutes

warmup.

EXT

TRIG

IN

IMn

.

17Br

I~___

TIMEB~E

RELEASE

LATCH

1985-3

Fig. 1-1.

Location

of

release

latch.

1-1

Operating

Instructions-7B50A

0-

1

:

& .

.,JU-I

---+fI.~

i'

@-+:H.-----"

I.

TRIGGERING

I I

MODE COUPLING

p.p AUTO

AC

~

[j

AUTO

AC

IF

REJ

SWP~'\

r-,J'I+--------

CAl

~

TEKTRONIX

®

7

SOURCE

INT

D

LINE

Fig. 1-2.

Front-panel

controls,

connectors,

and

indicators.

1-2

TRIGGERING

EXTERNAL

TRIGGER

INPUT

@

Operating

Instructions-7B50A

TRIGGERING

Q)

LEVEL

Control-Selects

a

point

on

the

trigger signal

where

triggering

occurs.

eD

SLOPE

Switch-Permits

sweep

to

be

triggered

on

negative

or

positivelloing

portions

of

the

trigger signal.

o

READY

Indicator-Illuminates

when

sweep

circuit

is

armed

(SINGLE

SWEEP

Mode).

o

TRIG'O

Indicator-Illuminates

when

the

display

is triggered.

CD

MODE Push

buttons-Selects

the

operating

mode

of

the

triggering

circuit.

CD

COUPLING

Push

buttons-Selects

the

method

of

coupling

the

trigger signal

to

triggering

circuit.

(j)

SOURCE

Push

buttons-Selects

source

of

the

trigger signal.

CD

@

®

@

®

SWEEP

POSITION

Control-Provides

horizontal

positioning.

FINE

Control-Provides

precise

horizontal

positioning.

MAG

Pushbutton-Selects

magnified

X10

or

unmagnified

sweep.

HOLD

OFF

Control-Permits

hold

off

period

to

be

varied

to

improve

trigger

stability

on

repetitive

complex

waveforms.

TIME/DIV

Selector-Selects

the

sweep

rate

of

the

sweep

generator.

VARIABLE

Control

and

CAL

Switch-Selects

calibrated

or

uncalibrated

sweep

rates.

Uncalibrated

sweep

rates

can

be

continuously

reduced

to

at

least

the

sweep

rate

of

the

position.

SWP

CAL

Adjustment-Compensates

for

basic

timing

changes

due

to

the

differences

in

sensitivity

of

mainframes

EXTERNAL

TRIGGER INPUT

@

EXT

TRIG

ATTENUATOR-Selects

attenuation

factor

for

external

trigger signals.

®

EXT

TRIG

IN

Connector-Connector

(BNC

type)

provides

input

for

external

trigger signals.

Fig.

1·2.

Front·panel

controls,

connectors,

and

indicators

(cont.).

1985·4

1-3

Operating

Instructions-7B50A

5.

Set

the

mainframe

vertical

and

horizontal

modes

to

dis-

play

the

plug-in

units

used

and

adjust

the

intensity

and

focus

for

a

well-defined

display.

See

the

oscilloscope

main-

frame

and

amplifier

unit

instruction

manuals

for

detailed

opera-ting

instructions.

Sweep

Functions

NORMAL

SWEEP.

Perform

the

following

procedure

to

ob-

tain

a

normal

sweep

and

to

demonstrate

the

function

of

the

1.

Perform

the

preceding

Setup

Procedure.

2.

Connect

a O.4-volt,

l-kilohertz

signal

from

the

main-

frame

calibrator

to

the

amplifier

unit

input.

3.

Set

the

amplifier

unit

deflection

factor

for

4 divisions

of

display.

4.

Adjust

the

LEVE L

control

for

a

stable

display.

5.

Turn

the

POSITION

control

and

note

that

the

trace

moves

horizontally.

6.

Turn

the

FIN E

control

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

CAL

screwdriver

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

+300 C).

8. Press

to

release

the

VARIABLE

(CAL IN)

control.

Turn

the

VARIABLE

(CAL IN)

control

fully

counterclockwise

and

note

that

the

displayed

sweep

rate

changes

to

at

least

the

TIME/DIV

switch

setting

(i.e., 2 milli-

seconds/division).

Press

the

VARIABLE

(CAL IN)

knob

in

to

the

cal

ibrated

position.

MAGNIFIED

SWEEP.

Perform

the

following

procedure

to

obtain

a

Xl

0

magnified

display

and

to

demonstrate

the

function

of

the

1.

Obtain

a

one

cycle

per

division

display

as

described

in

the

preceding

Normal

Sweep

procedure.

1-4

2. Press

to

release

the

MAG

button

(X

10).

Note

that

the

unmagnified

display

within

the

center

division

of

the

grati-

cule

is

magnified

to

about

10

divisions.

3. Press

the

MAG

button

(Xl).

Triggering

Functions

Perform

the

following

procedure

to

obtain

a triggered

sweep

and

to

demonstrate

the

functions

of

the

1.

Obtain

a

display

as

described

in

the

preceding

Normal

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

a

stable

display

can be

obtained

at

several

positions

of

the

HOLD

OFF

control.

Return

the

HOLD

OFF

control

to

the

fully

counterclockwise

(MIN)

position.

NOTE

The

HOLD

OFF

control

varies the sweep

hold-off

time

which

effectively

changes the

repetition-rate

of

the

horizontal

sweep signal. However,

its

pri-

mary

function

is

to

obtain

a stable

display

of

complex

waveforms

which

are

otherwise

difficult

to

trigger.

4.

Press

the

AC, AC HF

REJ,

and

DC

COUPLING

buttons

for

both

the

+

and

-

positions

of

the

SLOPE

switch

and

check

for

a

stable

display

(LEVEL

control

may

be

adjusted,

if

necessary,

to

obtain

a

stable

display).

5.

Apply

the

O.4-volt, 1

kilohertz

signal

from

the

main-

frame

calibrator

to

the

amplifier

unit

and

to

the

EXT

TRIG

IN

connector.

6.

Press

the

EXT

SOURCE

button

and

set

the

amplifier

unit

deflection

factor

for

a 4-division display.

7. Press

the

AC, AC HF

REJ,

and

DC

COUPLING

buttons

for

both

the

+

and

-

positions

of

the

SLOPE

switch

and

check

for

a

stable

display

(LEVEL

control

may

be

adjusted,

if

necessary,

for

a

stable

display).

@

8. Press

the

AC

COUPLING,

INT

SOURCE,

and

NORM

MODE

buttons.

Adjust

the

LEVEL

control

for

a

stable

display.

9. Press

the

AUTO

MODE

button

and

adjust

the

LEVEL

control

for

a

free·running

display.

10.

Press

the

NORM

MODE

button

and

check

for

no

display.

11.

Adjust

the

LEVE

L

control

for

a

stable

display

and

press

the

SINGLE

SWP MODE

button.

12.

Note

that

one

trace

occurs

when

the

RESET

MODE

button

is

pressed.

13.

Disconnect

the

mainframe

calibrator

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.

Note

that

one

trace

occurs

and

that

the

READY

indi-

cator

extinguishes

when

the

mainframe

calibrator

signal

is

reconnected

to

the

amplifier

unit

input.

GENERAL

OPERATING

INFORMATION

Triggering

Switch

Logic

The

MODE,

COUPLING,

and

SOURCE

push

buttons

of

the

TRIGGERING

switches

are

arranged

in a

sequence

which

places

the

most-often

used

position

at

the

top

of

each

series

of

push

buttons.

With

this

arrangement,

a

stable

display

can

usually

be

obtained

by

pressing

the

top

push

buttons:

pop

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

LEVEL

control

is

either

at

a

setting

outside

the

range

of

the

trigger

signal

applied

to

this

unit

from

the

vertical

unit,

the

trigger

signal

amplitude

is

in-

adequate,

or

its

frequency

is

below

the

lower

frequency

limit

of

the

AC

COUPLING

switch

position.

If

the

desired

display

is

not

obtained

with

these

buttons

pushed

in,

other

selections

must

be

made.

Refer

to

the

following

discussions

or

the

instruction

manuals

for

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.

@

Operating

Instructions-7B50A

POp

AUTO.

The

pop

AUTO

MODE

provides

a

triggered

dis-

play

at

any

setting

of

the

LEVEL

control

whenever

an

ade-

quate

trigger

signal

is

applied.

The

range

of

the

LEVEL

control

in

the

pop

AUTO

MODE

is

between

approximately

10%

and

90%

of

the

peak-to-peak

amplitude

of

the

trigger

signal.

The

LEVEL

control

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

in trigger-signal

amplitude.

Therefore,

if

the

LEVEL

control

is

set

to

start

the

waveform

display

at

a

certain

per-

centage

point

on

the

leading

edge

of

a

low-amplitude

signal,

it

triggers

at

the

same

percentage

point

on

the

leading edge

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-line

reference

trace

(TRIG'D

light

off).

When

an

ade-

quate

trigger

signal

is

again

applied,

the

free-running

condi-

tion

ends

and

a

triggered

display

is

presented.

The

pop

AUTO

MODE

is

particularly

useful

when

observing

a series

of

waveforms,

since

it

is

not

necessary

to

reset

the

LEVE

L

control

for

each

observation.

The

pop

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

LEVEL

control

whenever

an

adequate

trigger

signal

is

applied

(see Trigger Level discus-

sions).

The

TR

IG'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

runs

at

the

rate

indicated

by

the

TIME/DIV

switch

(TRIG'D

indicator

off).

An

ade-

quate

trigger

signal

ends

the

free-running

condition

and

a

triggered

display

is

presented.

The

sweep

also free

runs

at

the

rate

indicated

by

the

TIME/DIV

switch

when

the

LEVEL

control

is

at

a

setting

outside

the

amplitude

range

of

the

trigger

signal.

This

type

of

free-running

display

is

useful

when

it

is

desired

to

measure

only

the

peak-to-peak

amplitude

of

a signal

without

observing

the

waveshape

(such as

bandwidth

measurements).

NORMAL.

The

NORM MODE

provides

a

triggered

display

with

the

correct

setting

of

the

LEVEL

control

whenever

an

adequate

trigger

signal

is

applied.

The

TR

IG'D

light indi-

cates

when

the

display

is

triggered.

1-5

Operating

Instructions-7B50A

The

normal

trigger

mode

must

be used

to

produce

triggered

displays

with

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 in

amplitude,

waveshape,

or

repetition

rate, a

conventional

repetitive

type

display

may

produce

an

unstable

presentation.

Under

these

circumstances,

a

stable

display can

often

be

obtained

by

using

the

single-sweep

feature

of

this

unit.

The

single-sweep

mode

is

also useful

to

photograph

non-repetitive

or

unstable

displays.

To

obtain

a single-sweep

display

of

a

repetitive

signal, first

obtain

the

best

possible display in

the

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.

Further

sweeps

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

to

the

crt

persistence,

allow

the

display

to

disappear

before

pressing

the

SINGLE

SWP

RESET

button

again.

At

fast

sweep

rates, it

may

be diffi-

cult

to

view

the

single-sweep display.

The

apparent

trace

intensity

can

be increased

by

reducing

the

ambient

light

level

or

by

using a viewing

hood

as

recommended

in

the

mainframe

instruction

manual.

When using

the

single-sweep

mode

to

photograph

wave-

forms,

the

graticule

may

have

to

be

photographed

separately

in

the

normal

manner

to

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

button

only

once

for

each

waveform

unless

the

sig-

nal

is

completely

symmetrical.

Otherwise,

multiple

wave-

forms

may

appear

on

the

film.

For

random

signals,

the

lens

can

be left

open

until

the

signal triggers

the

unit.

Further

information

on

photographic

techniques

is

given in

the

appropriate

camera

instruction

manual.

Trigger

Coupling

The

TRIGGERING

COUPLING

push

buttons

select

the

method

in

which

the

trigger signal

is

connected

to

the

trig-

ger circuits. Each

position

permits

selection

or

rejection

of

some

frequency

components

of

the

signal

which

triggers

the

sweep.

AC. AC

COUPLING

blocks

the

dc

component

of

the

trig-

ger signal. Signals

with

low-frequency

components

below

about

30

hertz

are

attenuated.

In

general, AC

COUPLING

can

be used

for

most

applications.

However, if

the

signal

1-6

contains

unwanted

frequency

components

or

if

the

sweep

is

to

be triggered

at

a low

repetition

rate

or

dc

level,

one

of

the

other

COUPLING

switch

positions

will provide a

better

display.

AC

LF

REJ.

AC LF

REJ

COUPLING

rejects

dc,

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

useful

for

providing

stable

triggering if

the

trig-

ger signal

contains

line-frequency

components.

Also,

the

AC LF

REJ

position

provides

the

best

alternate-mode

verti-

cal displays

at

fast

sweep

rates

when

comparing

two

or

more

unrelated

signals.

AC

HF

REJ.

AC

HF

REJ

COUPLING

passes all low-

frequency

signals

between

about

30

hertz

and

50

kilohertz.

Dc

is

rejected

and

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

COUPLING

can

be

used

to

provide

stable

trigger-

ing

from

low-frequency

signals

which

would

be

attenuated

in

the

other

COUPLING

switch

positions. DC

COUPLING

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

setting

of

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

to

the

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

unit

or

by

the

mainframe;

see

the

instruction

manuals

for

these

instruments

for

more

information.

For

most

applica-

tions,

the

internal

source

can be used. However,

some

applications

require

special triggering

which

cannot

be ob-

tained

in

the

INT

position.

In

such cases,

the

LINE

or

EXT

positions

of

the

SOURCE

switches

must

be used.

LINE.

The

LINE

position

connects

a

sample

of

the

power-

line voltage

from

the

mainframe

to

the

trigger

circuit.

Line

triggering

is

useful

when

the

input

signal

is

time-related

(multiple

or

submultiple)

to

the

line

frequency.

It

is

also

useful

for

providing a

stable

display

of

a

line-frequency

component

in

a

complex

waveform.

@

EXTERNAL.

The

EXT

position

connects

the

signal

from

the

EXT

TRIG

IN

connector

to

the

trigger

circuit.

The

ex-

ternal

signal

must

be

time-related

to

the

displayed

wave-

form

for

a

stable

display.

An

external

trigger signal

can

be

used

to

provide

a

triggered

display

when

the

internal

signal

is

either

too

low

in

amplitude

for

correct

triggering

or

con-

tains

signal

components

on

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

TR

IG

IN

connector

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

in

the

circuit

to

be

examined

without

re-

setting

the

TRIGGERING

controls.

The

710

push

button

attenuates

the

external

trigger signal

by

a

factor

of

10.

Attenuation

of

high

amplitude

external

trigger signals

is

desirable

to

increase

the

effective

range

of

the

LEVEL

control.

Trigger Slope

The

TRIGGERING

SLOPE

switch

(concentric

with

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

a signal

appear

in

the

display,

the

setting

of

the

SLOPE

switch

is

often

unimportant.

How-

ever, if

only

a

certain

portion

of

a

cycle

is

to

be

displayed,

correct

setting

of

the

SLOPE

switch

is

important

to

provide

a

display

that

starts

on

the

desired

slope

of

the

input

signal.

Trigger Level

The

TRIGGERING

LEVEL

control

determines

the

voltage

level

on

the

trigger signal

at

which

the

sweep

is

triggered.

When

the

LEVEL

control

is

set

in

the

+ region,

the

trigger

circuit

responds

at

a

more

positive

point

on

the

trigger sig-

nal. When

the

LEVEL

control

is

set

in

the

-region,

the

trigger

circuit

responds

at

a

more

negative

point

on

the

trigger signal.

Figure

1-3

illustrates

this

effect

with

different

settings

of

the

SLOPE

switch.

To

set

the

LEVEL

control,

first

select

the

TRIGGERING

MODE,

COUPLING,

SOURCE,

and

SLOPE.

Then

set

the

LEVE L

control

fully

counterclockwise

and

rotate

it

clock-

wise until

the

display

starts

at

the

desired

point.

Horizontal

Sweep Rates

The

TIME/DIV

switch

provides

calibrated

sweep

rates

from

5

seconds/division

to

50

nanoseconds/division

in

a 1-2-5

@

Operating

Instructions-7B50A

sequence.

The

VARIABLE

TIME/DIV

control

must

be in

the

calibrated

position

and

the

MAG

switch

set

to

X1

to

obtain

the

sweep

rate

indicated

by

the

TIME/DIV

switch.

However,

the

mainframe

crt

readout

will

display

the

appro-

priate

sweep

rate.

The

VARIABLE

TIME/DIV

control

includes

a

two-position

switch

to

determine

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

uncalibrated

sweep

rates,

to

at

least

the

sweep

rate

of

the

position.

A

calibrated

sweep

rate

can

be

obtained

in

any

position

of

the

VAR

IABLE

control

by

pressing in

the

VAR

IABLE

con-

trol.

This

feature

is

particularly

useful

when

a

specific

un-

calibrated

sweep

rate

has

been

obtained

and

it

is

desired

to

switch

between

calibrated

and

uncalibrated

displays.

Time

Measurement

When

making

time

measurements

from

the

graticule,

the

area

between

the

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 line

and

adjust

the

TIME/DIV

switch

so

the

end

of

the

timing

area falls

between

the

second

and

tenth

vertical lines.

Sweep Magnification

The

sweep

magnifier

can

be used

to

expand

the

display

by a

factor

of

10.

The

center

division

of

the

unmagnified

display

is

the

portion

visible

on

the

crt

in

the

magnified

form

(see

Figure 1-5).

The

equivalent

length

of

the

magnified

sweep

is

more

than

100 divisions;

any

10 division

portion

can

be

viewed

by

adjusting

the

POSITION

and

FINE

POSITION

controls

to

bring

the

desired

portion

into

the

viewing area.

When

the

MAG

switch

is

set

to

X10 (OUT)

the

equivalent

magnified

sweep

rate

can

be

determined

by

dividing

the

TIME/DIV

setting

by

10;

the

equivalent

magnified

sweep

rate

is

displayed

on

the

crt

readout.

Variable

Hold

Off

The

HOLD

OFF

control

improves

triggering

stability

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 a

stable

display

cannot

be

obtained

with

the

TR

I

G-

GERING

LEVEL

control,

the

HOLD

OFF

control

can

be

varied

for

an

improved

display.

If

a

stable

display

cannot

be

obtained

at

any

setting

of

the

LEVEL

and

HOLD

OFF

con-

trols,

check

the

TRIGGERING

COUPLING

and

SOURCE

switch

settings.

1-7

Operating

Instructions-7B50A

TRuro

@1!,@1P1li

•

LEVEL

"/""

.............

+

f~

::~

.....

:,

••••

~(SLOPEI

(LEVELI~

CRT

DISPLAY

OBTAINED

WITH

SLOPE

SWITCH

SET

TO

POSITIVE

(+1

CRT

DISPLAY

OBTAINED

WITH

SLOPE

SWITCH

SET

TO

NEGATIVE

(-I

TRI&'O

@1!,@1P1li

•

LEVEL

U·~

©5

TRIG'O

,;i[l,@IPIli.

LEVEL

0°~

©J

TRIG'O

~1l,@1P1li

•

LEVEL

~o~

©J

••••

-

•••

f--

POSI~IVEI

(+1

SLOPE

/

J J

1\

I '\

I V \ I \ \

~!'-

1\

I \ 1 \ I

\J

J w \ J

POSITIVE

r-

(+1

SLOPE

/

{J

v

!f\

~

r

If\

" \ I

\.

I \

1\

r TI

1\

\/ J V

\J

1\/

NEGATIVE

~

lIH

SLOPE

? r

f\

~

r

f\

1

1.

\.

I

1.

11

I

\ I \ I \ I \

\~

\

IV

J \

NEGATIVE

(-I

SLOPE

I

1\

/ '\

f~

1\

\

V

.\.

t\

\

I \ \ \

\ V

IJ

\ \/

Fig. 1-3.

Effect

of

LEVEL

control

and

SLOPE

switch

on

crt

display.

1-8

1\

\

~

~~

\

I

11

I

J

C1985-6

@

Mainframe

Operating Modes

The

time-base

unit

can

be

operated

either

as an indepen-

dent

time

base

in

any

Tektronix

7000-series oscilloscope

mainframe,

or

as a

delayed-sweep

unit

in

those

mainframes

that

have

two

horizontal

compartments.

A

companion

de-

laying time-base

unit

is

required

for delayed-sweep

operation.

Refer

to

the

delaying time-base

unit

instruction

manual for

additional

information.

SECOND-VERTICAL

LINE

TENTH-VERTICAL

LINE

@

I I

I

----r----+---+---+---+---+---+---+-----~-

-----~-

I I

t-I".---TIME

MEASUREMENT

---t.~1

AREA

C1752-06

Fig. 1-4.

Area

of

graticule

used

for

most

accurate measurements.

Operating I

nstructions-7850A

l'ms

~

~ ~

~

f-

-

\ \

UNMAGNIFIED

D

ISPLAY

\ \

--

,r-"

-

\

, \

MAG-Xl

I \

, \ I

I

100

j.!.S

,

1\

I \

, \

I

1/

MAGNIFIED

DISP

LAY

MAG-Xl0

, I

1985-7

Fig. 1-5.

Operation

of

sweep

magnifier.

1-9

Operating Instructions-7B50A

APPLICATIONS

The

following

information

describes

procedures

and

techniques

for

making

basic

time

measurements

with

the

time-base

unit

installed

in

a

Tektronix

7000-series oscilloscope. These

procedures

provide

enough

detail

to

enable

the

operator

to

adapt

them

to

other

measurements.

Contact

your

Tektronix

Field Office

or

representative

for

assistance

in

making

measurements

that

are

not

described

in

this

manual.

TIME-INTERVAL

MEASUREMENTS

Since

time

is

a

function

of

the

sweep

rate

and

the

horizon-

tal

distance

(in divisions)

that

the

sweep

travels across

the

graticule

in

a

calibrated-sweep

oscilloscope

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-

characteristics

of

a

waveform

such

as

period,

frequency,

rise

time,

fall

time,

and

pulse

width.

The

procedure

for

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

a

displayed

waveform

can be

measured

with

basically

the

same

technique.

Period and Frequency Measurements

Perform

the

following

procedure

to

measure

the

period

and

determi

ne

the

frequency

of

a

displayed

waveform:

1. Install

the

time-base

unit

in

a

mainframe

horizontal

compartment

(either

A

or

B

horizontal

in a

four-compart-

ment

mainframe).

2.

Connect

the

signal

to

be

measured

to

the

vertical

unit

input.

3.

Set

the

mainframe

horizontal-

and

vertical-mode

switch-

es

to

display

the

time

base

and

vertical units. (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

a

stable

display (see General

Operating

Information

for

selecting

proper

triggering).

5.

Set

the

vertical

deflection

factor

and

position

control

for

about

a 5-division display, vertically

centered

on

the

graticule.

6.

Set

the

TIME/DIV

switch

and

POSITION

control

for

1

complete

cycle

displayed

within

the

center

8

graticule

divi-

sions as

shown

in

Figure 1-6.

1-10

7. Measure

the

horizontal

distance

in divisions over 1 com-

plete

cycle

of

the

displayed

waveform

(see Figure 1-6).

8. Multiply

the

horizontal

distance

measured

in

Step

7

by

the

TIME/DIV

switch

setting. (Divide

the

answer

by

10

if

sweep

magnification

is

used.)

Example:

Assume

that

the

horizontal

distance

over 1 com-

plete

cycle

is

7 divisions,

and

the

TIME/DIV

switch

setting

is.l

ms (see Figure 1-6).

Using

the

formula:

Period =

Horizontal

distance

X

TIME/DIV

setting

Magnification

Substituting

values:

Period = 7 X 0.1 ms

1

FREQUENCY

=

PERiOD

100

90

..

' .

'"

.

f-EU

~

I I

01 I

I

( I

I'"

.

'i'

.

..

/

t"--\

.

...

[7

"-

\

...

.

."

.

...

.

0.7

millisecond

.

...

. " .

...

.

..

rB~

~r\.i

~

II:

\ / I

I

. . . . 1'-.

V

..

.J

MEASURE

HORIZONTAL

DISTANCE

FROM

ATO

B

...

.

L

1/

.

...

1985-10

Fig.

'·6.

Measuring

the

period

and

determining

the

frequency

of

a

displayed

waveform.

@

9.

Determine

the

frequency

of

the

displayed

waveform

ob-

tained

in

steps

1

through

8 by

taking

the

reciprocal

of

the

period

of

1

cycle.

Example:

Assume

that

the

period

of

the

displayed

wave-

form

is

0.7

millisecond.

Using

the

formula:

Frequency

Substituting

values:

Frequency

=

Period

_1_

0.7

ms 1.43

kilohertz

Rise-Time

and

Fall-Time

Measurements

Perform

the

following

procedure

to

measure

the

rise

time

and

fall

time

of

a

displayed

waveform:

1. Install

the

time-base

unit

in

a

mainframe

horizontal

compartment

(either

A

or

B

horizontal

in

a

four-compart-

ment

mainframe).

2.

Connect

the

signal

to

be

measured

to

the

vertical

unit

input.

3.

Set

the

mainframe

horizontal-

and

vertical-mode

switch-

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.)

4.

Set

the

TRIGGERING

switches

and

LEVEL

control

for

a

stable

display

(see General

Operating

Information

for

selecting

proper

triggering).

5.

Set

the

vertical

deflection

factor

and

position

control

for

a

vertically-centered

display

with

an

exact

number

of

divisions

of

amplitude.

6.

Set

the

TIME/DIV

switch

and

POSITION

control

to

dis-

play

the

rising

or

falling

portion

of

the

waveform

within

the

center

8

graticule

divisions as

shown

in

Figure

1-7 (see

General

Operating

Information

in

this

section

for

discussion

of

timing

measurement

accuracy).

7.

Determine

rise

time

or

fall

time

by

measuring

the

hori-

zontal

distance

in

divisions

between

the

point

on

the

rising

@

10

o·

0

10

9

I

0

I

Operating

Instructions-7B50A

RISE

TIME

~

.

..

....

..\=~

Vi

I

7

~

!

~

V i

~

..

.

I'

.

..

. . .

..

I

MEASURE

HORIZONTAL

DISTANCE

FROM

1

A

TO

B (10%

TO

90%) ,

FALL

TIME

I~

P

..

...

.

...

.

..

....

"-

~

~\

I \

:

I K

I

t;~

I \

lf~

I

.~

,"

..

...

.

...

.

..

. " . .

...

,

MEASURE

HORIZONTAL

DISTANCE

FROM

A

TO

B (90%

TO

10%)

1985-11A

Fig. 1-7.

Measuring

the

rise

time

and

fall

time

of

a

displayed

wave-

form.

or

falling

portion

of

the

waveform

that

is

10%

and

the

point

that

is

90%

of

the

total

display

amplitude

(see Figure

1-7).

NOTE

The

left

edge

of

the

oscilloscope

graticule

is

scribed

with

0,

10,90,

and

100% lines

for

con-

venience when measuring rise

time

or

fall

time.

To

use

this feature,

adjust

the vertical

deflection

factor

and

position

control

to

fit

the

display

be-

tween

the

0

and

100%

graticule

lines. Then

measure the

horizontal

distance between the

points

where the waveform crosses the

10%

and

90%

graticule

lines.

1-11

Tektronix 7B50A User manual