Tektronix 3B4 Manuel utilisateur

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INSTRUCTION

MIAN

UAL

Serial

Number

Tektronix,

Inc.

S.W.

Millikan

Way

@

P.

O.

Box

500

®

Beaverton,

Oregon

97005

@

Phone

644-0161

@

Cables:

Tektronix

070-431

964

SECTION

1

CHARACTERISTICS

Introduction

The

Type

3B4

Time

Base

plug-in

unit

is

designed

to

be

used

primarily

with

the

Tektronix

Type

561A

Oscilloscope

sys-

tem;

however,

It

can

also

be

used

with

the

other

560-Seriés

systems

that

use

3B-Series

plug-in

units

such

as

the

Type

564

and

Type

567.

As

part

of

an

oscilloscope

system,

the

Type

3B4

is

used

as

an

accurate

time

base

generator

or as

a

calibrated

amplifier

for

externally

generated

deflection

sig-

nals,

When

used

with

the

567

or

RM567,

the

3B4

provides

a

time-

base,

but

does

not

activate

the

digital

readout

circuitry.

In

the

565

or

RM565,

the

3B4

provides

a

vertical

time-base

for

raster

applications

but

does

not

provide

retrace

blanking.

The

Type

3B4

provides

calibrated

sweep

rates

from

0.05

psec/div

to

5sec/div

in

25

calibrated

steps.

A

five-step,

direct-reading

magnification

feature

provides

magnification

up

to

40X

or

50X,

depending

on

the

sweep

rate

to

which

magnification

is

applied.

When

the

Type

3B4

is

used

as

an

amplifier

for

externally

generated

deflection

signals,

the

magnifier

provides

five

steps

of

deflection

sensitivity,

from

0.2

volts/div

to

5

volts/div.

In

addition,

a

variable

control

provides

uncalibrated

sweep

rates

and

deflection

sensitivities

between

the

calibrated

steps.

By

using

the

variable

control,

uncalibrated

sweep

rates

from

0.05

psec/div

to

approxi-

mately

12.5

sec/div

and

deflection

sensitivites

from

0.2

volts/

div

to

approximately

12.5

volts/div

are

available.

Uncali-

brated

operation

is

indicated

by

a

neon

lamp.

Normally,

the

Type

3B4

is

inserted

in

the

right-hand

com-

partment

(operator's

right,

oscilloscope’s

left)

of

the

oscillo-

scope

and

in

this

position

provides

horizontal

deflection.

When

used

with

the

Type

561A,

the

Type

3B4

can

be

inserted

into

the

left-hand

compartment

of

the

oscilloscope

to

provide

a

time

base

that

runs

vertically

on the

crt

screen.

Due

to

differences

in

the

horizontal

and

vertical

deflection

plate

sensitivities,

the

Type

3B4

must

be

calibrated

for

vertical

deflection

use

if

accuracy

is

required

in

such

application.

This

manual

is

written

with

the

assumption

that

the

Type

3B4

will

normally

be

used

to

provide

horizontal

deflection

sig-

nals

in

a

Type

561A.

Triggering

Facilities

TRIGGER

MODE

Switch

Free

Run,

Auto,

Normal,

and

Single

Sweep

TRIGGERING

LEVEL

Con-

See

Tables

1-1

and

1-2.

trol

SLOPE

Switch

+

or

—

COUPLING

Switch

Ac,

Ac

Low-Frequency

Re-

ject,

and

Dc

SOURCE

Switch

Internal,

Line,

External,

and

External

+

10

TRIGGERING

LEVEL

Control

Voltage

Range

(external

triggering}

See

Table

1-1.

TABLE

1-1

Voltage

Range

SOURCE

COUPLING

Typical

Minimum

AC,

DC

or

EXT

AC

LF

REJ

+19

¥

+15

AC

or

DC

+190

v

EXT

+

10

AC

LF

REJ

+150

v

NOTE

The

voltage

range

of

the

TRIGGERING

LEVEL

con-

trol

indicates

the

maximum

external

peak

voltage

that

will

permit

triggering

at

any

amplitude

point

on

the

signal.

Signals

with

greater

amplitudes

can

be

used

and

will

provide

triggering,

but the

range

of

trigger-point

selection

is

still

limited

to

the

TRIG-

GERING

LEVEL

control

voltage

range.

Triggering

Sensitivity.

See

Table

1-2.

@1

TABLE

1-2

SOURCE

Voltage

Range

AC

AC

LF

REJ

DC

INT

1

minor

division

of

deflection

30

cps

to

20

mc.

Outside

these

limits

requires

larger

triggering

signal.

1

minor

division

of

deflection

30

kc to

20

mc.

Outside

these

limits

requires

larger

triggering

signal.

1

minor

division

of

deflection

dc

to

20

me

(with

trace

verti-

cally

centered},

Above

20

mc

requires

larger

triggering

signal,

EXT

0.5v

30

cps

fo

20

mc.

Outside

these

limits

requires

larger

trig-

gering

signal.

0.5v

30kc

to

20mc.

Outside

these

limits

requires

larger

trig-

gering

signal.

0.5v

dc

to

20mc.

(with

trace

vertically

centered).

Above

20

mc

requires

larger

triggering

signal.

1-1

Characteristics—Type

3B4

Automatic

Triggering.

In

this

mode

of

operation

a

bright-line

sweep

is

displayed

automatically

in

the

absence

of

a

trigger.

The

sweep

triggering

characteristics

stated

pre-

viously

also

apply

for

automatic

triggering

except

that

the

triggering

signal

must

be

higher

than

about

20cps.

The

TRIGGERING

LEVEL

control

operates

when

a

triggering

sig-

nal

is

present.

Single

Sweep.

This

feature

permits

only

one

triggered

sweep

following

each

reset

pulse.

The

reset

pulse

is

gen-

erated

by

pressing

the

PUSH

TO

RESET

button.

The

trigger-

ing

characteristics

stated

previously

apply.

EXT

TRIG

IN

Connector

Input

Characteristics.

See

Table

1-3.

TABLE

1-3

TRIG

729

fe)

Rp

|

—0o

ot

Rp

Input

SOURCE

|

COUPLING|

C,

C,

{Meg

©)

{Voltage

(pf)

Max

Peak

DC

220

[shorted

[

~1

+75

EXT

AC

20

|=0.01

ph]

=

+500

AC

LF

REJ

|

=20

|100

pf

|

0.09

|

+500

EXT

DC

=

shorted

|

10

500

+

AC

=

20.01

wf}

10

+500

10

AC

LF

REJ

|

20

|=100pf

|

=

+500

Sweep

Facilities

TIME/DIV

0.2

psec/div

to

Ssec/div

in

23

steps,

I,

Switch

2,

5

sequence.

The

calibration

accuracy

(unmagnified)

is

3%

from

0.2

wsec/div

to

2

sec/div;

5%

at

5

sec/div.

VARIABLE

Uncalibrated

variable

time/div

control.

Control

Multiplies

the

sweep

time/div

of

any

step

of

the

TIME/DIV

switch

by

a

factor

vari-

able

from

1

to

>2.5.

POSITION

Coarse

horizontal

positioning

to

position

Controls

any

portion

of

the

trace

to

the

center

of

the

crt.

The

FINE

control

has

a

range

of

about

2

minor

divisions.

MAGNIFIER

Provides

direct

readout

magnification

of

Control

the

sweep

(up

to

50°).

The

magnifier

also

provides

the

0.05

and

0.1

psec/div

sweep

rates.

Magnified

sweep

accuracy,

—-5%

(exception:

5

sec/div).

Magnified

sweep

registration,

+1

minor

division,

1-2

+

GATE

OUT

Provides

a

+20-volt

(+15%)

output

pulse

Connector

during

sweep

time.

Sweep

Length

10.5

+0.3

major

division.

Sweep

Amplifier

(when

used

as

an

external

hori-

zontal

amplifier)

Facilities

HORIZONTAL

Calibrated

volts/div

steps

of

0.2,

0.5,

1,

VOLTS/DIV

2,

and

5

volts/div.

Accuracy

+3%

when

Switch

calibrated

to

match

the

oscilloscope

in

which

used.

The

amplifier

is

de

coupled

to

the

EXT

HORIZ

IN

connector.

VARIABLE

Multiplies

volts/div

of

any

step

by

a

factor

Control

variable

from

1

to

>2.5.

EXT

HORIZ

Input

R

and

C

is

typically

1

megQ

shunted

IN

Con-

by

40

pf.

nector

Frequency

De

to

400

kc.

Response

<30%

down

at

Response

400

ke

with

the

VARIABLE

control

set

to

CALIB

position.

Maximum

Input

+20

volts

dc,

or

20

volts

peak

ac.

Voltage

Environmental

Operating

TEMPERATURE

0°

C

to

+50°

C.

ALTITUDE

10,000

feet

maximum.

VIBRATION

0.015

inch

peak-to-peak,

(1.9

Gs)

for

15

minutes

along

each

axis.

Vibration

fre-

quency

varied

from

10-50-10

cps

in

1-

minute

cycles.

Non

Operating

TEMPERATURE

—35°

C

to

+60°

C.

ALTITUDE

50,000

feet

maximum.

VIBRATION

—0,015

-£0.003

inch

total

displacement

from

10

to

5

cycles.

TRANSIT

Meets

National

Safe

Transit

type

of

test

when

factory

packaged:

Vibration

for

one

hour

at

slightly

greater

than

1G.

30-inch

drops

on

corners,

edges

and

flat

surfaces.

Mechanical

Construction

Aluminum-alloy

chassis

with

chrome-plated

side

rails.

Front

panel

is

photo-etched

and

anodized.

Dimension

6%,

inches

high,

4%,

inches

wide,

147,

(approx.)

inches

deep

(overail).

Net

Weight

4.5

pounds.

Accessories

Information

on

accessories

for

use

with

this

instrument

is

included

at

the

rear

of

the

mechanical

parts

list.

—

SECTION

2

OPERATING

INSTRUCTIONS

Front-Panel

Controls

and

Connectors

See

Fig. 2-1.

NOTE

A

more

complete

description

of

the

controls

and

connectors

is

included

under

‘‘Standard

Sweep

Op-

eration”

later

in

this

section.

TRIGGER

MODE

Selects

the

manner

in

which

the

Time

Base

Switch

FREE

RUN

AUTO

NORM

SINGLE

SWEEP

and

PUSH

TO

RESET

SOURCE

INT

LINE

EXT

and

EXT

+

10

COUPLING

AC

AC

LF

REJ

DC

sweeps

are

initiated.

For

example:

In

this

position,

recurrent

sweeps

are

pro-

vided.

The

completion

of

one

sweep

causes

the

next

to

begin.

Automatic

sweep.

Permits

each

sweep

to

be

triggered

when

the

triggering-signal

repetition

rate

is

about

20

cps

or

greater.

For

lower

repetition

rates

or

in

the

absence

of

a

triggering

signal,

the

sweeps

are

recurrent,

as

in

the

FREE

RUN

posi-

tion.

Normal

method

of

operation.

Each

sweep

is

triggered

by

the

signal

from

the

inter-

nal

trigger

generator,

Often

used

when

displays

of

non-repetitive

signals

are

photographed.

When

the

lamp

inside

the

PUSH

TO

RESET

button

is

lit,

the

time

base

is

ready

to

produce

one

trig-

gered

sweep.

Selects

the

source

of

the

triggering

signal:

Internal.

Obtains

the

sweep

triggering

signal

from

the

vertical

plug-in

unit.

Obtains

the

sweep

triggering

signal

from

a

low-voltage

winding

on

the

oscilloscope

power

transformer.

Permits

external

signals

applied

to

the

EXT

TRIG

IN

connector

to

be

used

for

sweep

triggering.

High-amplitude

_

trig-

gering

signals

can

be

attenuated

by

using

the

EXT

+

10

position.

Permits

acceptance

or

rejection

of

some

triggering

signal

characteristics:

Rejects

dc

and

attenuates

very

low-fre-

quency

ac

triggering

signals.

Ac

low-frequency

reject.

Rejects

de

and

discriminates

against

low-frequency

ac

triggering

signals.

The

30%

down

point

is

17

ke.

Accepts

ac

and

dc

triggering

signals,

SLOPE

(+

or

—)

Determines

whether

triggering

will

occur

during

the

positive-going

(+)

or

negative-

going

(—)

portion

of

the

triggering

signal.

TRIGGERING

LEVEL

TIME/DIV

OR

HORIZONTAL

VOLTS/DIV

MAGNIFIER

VARIABLE

&

Selects

the

amplitude

point

on

the

trigger-

ing

signal

where

triggering

will

occur.

Provides

23

calibrated

display

sweep

rates

(unmagnified}.

See

Fig.

2-1.

The

number

opposite

the

dot

on

the

MAGNIFIER

knob

skirt

always

indicates

the

sweep

time

per

centimeter

as

long

as

the

VARIABLE

con-

trol

is

in

the

CALIB

position.

The

number

bracketed

by

the

two

heavy

black

lines

on the

clear

plastic

knob

flange

is

the

un-

magnified

sweep

time

per

division.

To

change

the

unmagnified

sweep

rate,

the

concentric

flange

and

the

MAGNIFIER

knob

must

first

be

interlocked

by posi-

tioning

the

dot

on

the

MAGNIFIER

knob

between

the

two

heavy

black

lines

on

the

flange.

When

the

flange

is

positioned

so

that

the

two

black

lines

bracket

the

EXT

HORIZ

IN

position,

any

signal

connected

to

the

EXT

HORIZ

IN

connector

is

applied

to

the

horizontal

amplifier.

In

this

position

of

the

switch,

the

amplified

externally

generated

signal

provides

horizontal

de-

flection.

Provides

magnification

of

the

time

base

display

up

to

40X

or

50X

in

five

direct-

reading

steps

(Magnification

of

the

four

fastest

unmagnified

sweep

rates

is

limited

to

0.05

psec/div).

For

example,

at

10

magnification,

the

5

minor

division

seg-

ment

at

the

center

of

an

unmagnified

crt

display

is

horizontally

expanded

to

full

graticule

width.

Any

other

5

minor

divi-

sion

segment

of

the

original

unmagnified

display

may

then

be

observed

in

magnified

form

by

turning

the

POSITION

controls.

To

determine

the

degree

of

magnification,

divide

the

number

bracketed

by

the

two

black

lines

on

the

clear

plastic

flange

by

the

number

adjacent

to

the

dot

on

the

MAGNIFIER

knob.

Provides

continuously

variable

uncalibrated

sweep

rates

between

about

0.4

and

1.0

times

that

indicated

by

the

TIME/DIV

switch.

Whenever

the

VARIABLE

knob

is

not

set

to

CALIB,

the

UNCAL

lamp

lights.

When

the

TIME/DIV

switch

is

set

to

the

EXT

HORIZ

IN

position,

the

VARIABLE

knob

provides

~

2.5:1

change

in

horizontal

amplifier

sensitivity.

STANDARD

SWEEP

OPERATION

The

control

and

switch

settings

listed

under

‘First-Time

Operation"

later

in

this

section

establish

the

basic

condi-

tions

necessary

for

most

measurements.

In

many

applications,

it

is

desirable

for

a

repetitive

signal

to

produce

a

stationary

2-1

Operating

Instructions—Type

3B4

2-2

TYPE

3B4

TIME

BASE

FINE

VARIABLE

POSITION

TIME/DIV

or

Tite

HORIZONTAL

VOLTS/DIV

2

VOLTS/DIV

PULL

MAG

TRIGGER

MODE

AUTO

NORM

FREE

RUN

SLOPE

COUPLING

SOURCE

TRIGGERING

AC

INT

EXT

LEVEL

Fig

2-1.

Front

Panel

Controls

and

Connectors

_——

——

display

on

the

crt

so

the

waveform

can

be

examined

in

detail. For

this

type

of

display,

the

start

of

each

sweep

must

bear

a

definite

fixed-time

relationship

to

the

events

in

the

input

signal.

This

can

be

accomplished

by

using

the

displayed

signal

or

another

related

signal

to

start

(trigger)

single

or

repetitive

sweeps.

The

following

is

a

detailed

description

of

the

control

and

switch

settings

which

provide

complete

control

over

the

means

of

triggering

the

sweep.

It

is

assumed

that

the

oscilloscopes system

is

a

Tektronix

Type

561A.

TRIGGER

MODE

FREE

RUN.

Free-running

operation

produces

continuously

repetitive

sweeps

even

in

the

absence

of

a

triggerifg

signal.

These

sweeps

provide

a

reference

trace,

as

does

the

AUTO

position.

This

method

of

operation

is

useful

in

applications

where

a

device

under

test

requires

a

trigger

or

input

signal.

The

front-panel

+GATE

OUT

signal

may

be

used

to

operate

the

device

under

test.

The

resulting

signal

displayed

on

the

crt

will

then

be

synchronized

with

the

sweep.

AUTO.

This

position

is

frequently

used

for

ease

of

opera-

tion

and

because

of

the

reference

trace

produced

in

the

absence

of

a

triggering

signal.

The

time

base

free

runs

with-

out

the

application

of

a

trigger.

If

a

triggering

signal

is

received,

the

free

running

is

interrupted,

but

this

first

event

in

the

signal

does

not

trigger

a

sweep.

If

the

first

signal

event

is

followed

by

a

second

event

within

about

80

msec,

a

triggered

sweep

is

initiated,

and

if

not,

the

free

running

resumes,

Since

the

dormant

period

is

limited

to

about

80

msec,

signal

frequencies

below

about

20

cps

cannot

produce

a

triggered

sweep

in

the

AUTO

mode.

For

such

signals,

the

NORM

mode

of

operation

is

used.

With

the

SOURCE

switch

set

to

INT

and

the

TRIGGER

MODE

switch

set

to

AUTO,

the

sweep

will

trigger

on

any

signal

that

will

trigger

the

NORM

mode

(about

1

minor

division

of

deflection)

so

long

as

the

triggering

signal

is

above

about

20

cps.

When

operating

in

the

AUTO

mode,

it

is

necessary

to

adjust

the

TRIGGERING

LEVEL

contro!

to

lock

the

sweep

with

the

triggering

signal.

NORM.

In

the

NORM

or

normal

mode,

the

time

base

is

dormant

in

the

absence

of

a

triggering

signal.

Each

sweep

must

be

initiated

by

a

triggering

signal.

SINGLE

SWEEP.

Single

sweep

is

often

used

when

photo-

graphing

non-reptitive

waveforms

and

in

other

applications

where

the

vertical

input

signal

continually

varies

in

amplitude

shape,

or

time

interval.

A

continuous

display

of

such

signals

would

appear

as

a

jumbled

mixture

of

many

different

waveforms

and

would

yeild

little

or

no

useful

information.

The

Type

3B4

permits

a

single

sweep

to

be

presented

with

the

elimination

of

all

subsequent

sweeps.

The

information

in

the

one

sweep

is

thus

clearly

recorded

without

the

con-

fusion

resulting

from

multiple

nonrepetitive

traces.

When

the

TRIGGER

MODE

switch

is

set

to

SINGLE

SWEEP,

the

time

base

becomes

inoperative.

The

time

base

can

be

“reset”

to

the

triggerable condition

by

pressing

the

RESET

button.

If

there

is

sufficient

delay

before

triggering,

the

RESET

lamp

will

light

to

show

that

the

time

base

is

ready

to

be

triggered.

When

the

time

base

has

been

triggered

and

one

sweep

completed,

the

time

base

again

becomes

inopera-

tive

and

the

lamp

extinguishes.

@

Operating

Instructions—Type

3B4

SOURCE

INT.

It

is

usually

easiest

to

obtain

the

sweep

triggering

signal

internally

(INT)

from

the

vertical

deflection

system.

LINE.

If

the

displayed

signal

frequency

is

related

to

the

power-line

frequency,

the

line

source

can

be

used.

This

source

is

useful

when

the

displayed

signal

does

not

allow

internal

triggering.

EXT.

External

triggering

is

often

used

when

signal

tracing

in

amplifiers,

phase-shift

networks,

and

wave-shaping

circuits.

The

signal

from

a

single

point

in

the

circuit

can

be

connected

to

the

EXT

TRIG

IN

connector

through

a

signal

probe

or

a

cable.

With

this

signal

triggering

the

sweep,

it

is

possible

to

observe

the

shaping,

amplification,

and

time

relationship

of

a

signal

at

various

points

in

the circuit

without

resetting

the

triggering

controls.

EXT.

+

10.

The

only

difference

between

external

(EXT)

and

external

divided-by-10

{EXT

+

10)

is

that

the

latter

attenuates

the

external

triggering

signal.

Attenuation

of

high-

amplitude

external

triggering

signals

is

desirable

to

broaden

the

TRIGGERING

LEVEL

contro!

range.

DC.

De

coupling

allows

the

trigger

circuits

to

receive

signals

of

all

frequencies

from

de

upward.

It

is

best

to

de

couple

for

very

low-frequency

signals

(below

about

20

cps).

AC.

Ac

coupling

rejects

the

de

component

of

triggering

signals

and

increasingly

attenuates

ac

triggering

signals

as

the

frequency

decreases.

This

position

of

the

coupling

switch

is

not

normally

used

for

triggering

signals

below

about

20

cps,

but

this

is

the

most

used

position

of

the

switch.

AC

LF

REJ.

Ac

low-frequency

reject

coupling

rejects

the

dc

component

of

triggering

signals

and

increasingly

attenu-

ates

ac

signals

as

frequency

decreases

(30%

down

point

17

ke).

If

line-frequency

hum

is

mixed

with

a

desired

high-

frequency

triggering

signal,

best

results

are

obtained

by

using

this

position

of

the

COUPLING

switch.

Ac

low-frequency

reject

coupling

should

also

be

used

when

triggering

internally

from

multi-trace

plug-in

units

operated

in

the

alternate-trace

mode

(unless

the

“trigger

from

a

single

channel

only”

feature

of

the

plug-in

is

used).

For

additional

information,

see

the

multi-trace

vertical

plug-

in

unit

instruction

manual.

SLOPE

Sweeps

can

be

triggered

during

either

the

rising

or

falling

portion

of

the

triggering

signal.

When

the

display

consists

of

several

cycles

of

the

input

signal,

either

setting

of

the

SLOPE

switch

may

be

used.

However,

if

it

is

desired

to

display

less

than

one

full

cycle

of

the

input

signal,

the

SLOPE

switch

permits

the

sweep

to

start

on

either

the

rising

(+

slope)

or

falling

(—

slope).

TRIGGERING

LEVEL

The

TRIGGERING

LEVEL

control

determines

the

instanta-

neous

voltage

on

the

triggering

signal

at

which

the

sweep

is

triggered,

(This

instantaneous

voltage

can

also

include

a

dc

2-3

Operating

Instructions—Type

3B4

level

if

the

COUPLING

switch

is

set

to

DC.)

With

the

SLOPE

switch

at

+,

adjusting

the

TRIGGERING

LEVEL

control

makes

it

possible

to

trigger

the

sweep

consistently

at

virtually

any

point

on

the

positive

slope

of

the

triggering

signal.

Like-

wise,

with

the

SLOPE

switch

at

—,

adjusting

the

TRIGGER-

ING

LEVEL

control

makes

it

possible

to

trigger

at

virtually

any

point

on

the

negative

slope

of

the

triggering

signal.

TIME/DIV

OR

HORIZONTAL

VOLTS/DIV

The

Time

Base

has

23

calibrated

sweep

rates

ranging

from

0.2

usec/div

to

5sec/div

(unmagnified

}.

See

Fig,

2-2.

The

number

opposite

the

dot

on

the

MAGNIFIER

knob

indicates

the

sweep

time

per

division

as

long

as

the

VARIABLE

con-

trol

is

in

the

CALIB

position,

The

unmagnified

sweep

rate

value

being

used

appears

between

the

two

black

lines

on

the

clear

plastic

flange

of

the

TIME/DIV

control.

The

VARI-

ABLE

control

and

MAGNIFIER

switch,

used

in

conjunction

with

the

TIME/DIV

switch,

permit

the

sweep

rate

to

be

varied

continuously

between

50

nsec/div

and

about

12.5

sec/div.

The

MAGNIFIER

switch

is

discussed

under

“MAGNIFIER”.

All

sweep

rates

obtained

with

the

VARIABLE

control

in

any

but

the

fully

clockwise

position

are

uncalibrated,

Uncali-

brated

sweep

rates

are

indicated

when

the

UNCAL

lamp

is

lit.

VARIABLE

TIME/DIV

or

YNPAS

HORIZONTAL

VOLTS/DIV

|

ExT

HORIZ

IN

Fig.

2-2.

TIME/DIV

OR

HORIZONTAL

VOLTS/DIV

and

MAGNIFIER

KNOBS.

When

the

flange

is

positioned

so

that

the

two

heavy

black

lines

bracket

the

EXT

HORIZ

IN

position

the

horizontal

am-

plifier

input

is

connected

to

the

EXT

HORIZ

IN

connector

and

accepts

external

horizontal

deflection

signals,

In

this

mode

of

operation,

five

ranges

of

horizontal deflection

sen-

sitivity

are

available.

The

five

sensitivity

ranges

are

from

0.2

volts/div

to

5

volts/div.

To

position

the

TIME/DIV

switch

to

the

EXT

HORIZ

IN

position,

turn

the

MAGNIFIER

knob

until

the

dot

on

the

knob

2-4

is

positioned

between

the

two

black

lines

on

the

clear

plastic

flange.

Turn

the

knob

until

the

two

black

lines

on the

flange

bracket

the

position

marked

“EXT

HORIZ

IN".

The

external

horizontal

deflection

sensitivity

may

now

be

selected

by

pulling

the

MAGNIFIER

knob

outward

to

unlock

it,

then,

while

holding

the

knob

out,

turn

it

to

the

desired

volt/div

position,

MAGNIFIER

The

sweep

ranges

between

5

sec/div

and

2

usec/div

can

be

magnified

up

to

40

or

50

in

5

steps.

The

degree

of

magnification

is

the

ratio

between

the

indicated

magnified

rate

(number

opposite

the

dot

on

the

skirt of

the

MAGNI-

FIED knob)

and

the

indicated

unmagnified

rate

(number

bracketed

by

two

black

lines

on

the

clear

plastic

flange).

Since

the

magnified

display

rate

is

always

direct

reading,

it

is

seldom

necessary

to

determine

the

actual

magnifying

factor

used.

Above

2

ysec/div

the

number

of

steps

of

magnification

decrease

until

at

the

.2

uSEC

setting

of

the

TIME/DIV

switch

only

two

steps

of

magnification

are

available.

The

.2

.SEC

postion

is

the

highest

sweep

rate

to

which

the

TIME/DIV

switch

can

be

set,

but

by the use

of

the

two

additional

mag-

nified

positions,

and

effective

sweep

rate

of

50

nSEC/DIV

is

obtained.

FIRST-TIME

OPERATION

The

following

contro!

and

switch

settings

for

the

Type

3B4

can

be

used

for

a

wide

range

of

measurements,

The

operating

conditions

established

by

these

settings

also

pro-

vide

a

starting

point

for

the

operator

who

is

learning

to

use

the

instrument.

TRIGGER

MODE

AUTO

COUPLING

AC

SOURCE

INT

VARIABLE

(TIME/DIV}

CALIB

[fully

clockwise}

MAGNIFIER

Locked

to

TIME/DIV

switch

The

Type

384

now

provides

the

time

base

for

measure-

ments

of

vertical

deflection

signals

above

about

20

cps.

In

many

cases,

only

the

TIME/DIV

switch

and

the

TRIGGER-

ING

LEVEL

control

require

readjustment

when

progressing

from

one

measurement

to

the

next.

The

appropriate

TIME/DIV

switch

setting

depends

on

the

frequency

of

the

applied

signal

and

the

type

of

measurement.

For

example,

to

observe

about

2

cycles

of

the

oscilloscope

60

cycle

Calibrator

signal,

set

the

TIME/DIV

switch

to

5

mSEC.

The

following

conditions

must

exist

to

obtain

a

triggered

display

of

the

vertical

deflection

signal

with

the

preceding

control

settings:

1.

The

frequency

of

the

vertical

deflection

signal

must

be

about

20

cps

or

greater

(below

20

cps,

the

TRIGGER

MODE

switch

must

be

set

to

NORM).

2.

At

SOke

the

vertical

deflection

amplitude

must

be

at

least

1

minor

division.

See

Table

1-2.