BRUEL & KJAER 1022 - Description of the Beat Frequency Oscillator; General Description

BRUEL & KJAER 1022

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Description

General.

The

Beat

Frequency

Oscillator

Type

1022 is

primarily

designed

for

electrical

and

electro-acoustical

measurements.

It

works

on

the

heterodyne

principle

using

two

bigh

frequency

oscillators,

o

'ch

o

erates

on

a

fixed

frequenc

while

the

f

uency

of

the

other

can

be

altered

b a

variable

ca

acitor,

The

required

audio

frequency

IS

en

obtained

as

the

difference

between

the

hvo

~igh

frequencies

and

can

~~_!_~:ld

off

a

large

illuminated

~c

-

~

~

~

~

th~p~i

nter

~f

-

whichTs

-

c

-

~

-

~~~de(Ct~

-

th

-

;

-

vari

_

~Qle

~

capa:!~Jjie

:O

S.ci~1s

lo~arit~

~g~aduated

from

20

to

20oo;;

-·

c/

s.

An

INCREMENTAL

SCALE

is

also

provided,

allowing

exact

frequency

selection

~

in

the

range

- 50

to

+50

c/s

around

any

setting

on

the

main

scale.

The

zero-adjustment

is

controlled

by

-

~~~

inin

[3_~

-

~.ll

_

Ll)

_

Ert_w_e_en_j

h.e.-f.l:eq-t!.m

G-y

'

of

the

__

!fiains

voltage,

and

that

of

-

th~

--

<>.~<:?i!!~!9

_

~

volta~e

.

occuring

w~

~

-

~

__

the

--

~~ii

-

la!Qr._i;_i;med

.to

±hi

lr~q~

-

~~~y

-

~f

the

mains

;~d

--

th~

--:

p

-

ress

~

~tton

-

~arked

PoWER

FREQUEN

cv BEA-T

~~

~_i!l

_

t:

__

frunLl>_a

neL;;

Ti~~ii~"}

~

-

presse~.

The

variable

capacitor

has

two

control

knobs,

one

of

which

is

in

a

fixed

position

on

the

capacitor

spindle

and

is

used

for

quick

setting

to

the

de-

sired

freguency

..

The

other

will

,

when

depressed,

rotate

the

spindle

\vith

a

_r.a_tio

of

1,

to

5

giving

greater

accuracy

and

fine

selection

of

the

frequency.

A

worm

gear

permits

the

~:l__Eac

itor

to

be

tuned

automa~

.

!~

-

~

!!L

_

Jor

example,

with

the

aid

of

the

motor

of

the

Level

Recorder

Type

2305.

The

mechanical

connect:rorl

-

To

-

Tl1e

--

Levcl

___

Re-

corder

-is

effected

by

means

of

a

fl

~~~

haft

.

'-------------·-··-

···-·-

·-··· -

------

..

·-··· .. ···- . •

..

' . . .

.,

which

can

be

screwed

onto

the

bushing

on

the

side

of

the

Oscillator's

cabinet.

The

-

worm

g;;~~

-

~~-;_:;

-

b

-

e

--

enga:gea

-·

a

nd

rele

{\

-

sed

--

w1ill11i

e -

aTCi

___

o

f'

_a. buil't

-=-

i;

electromagnetic

clutch,

operated

from

a

switch

on

the

front

panel

marked

AUTOMATIC

SCANNING,

or

by

a

remote

control

arrangement.

The

electro-

-

magnetic

clutch

is a

friction-device

allowing

manual

tuning

of

the

variable

capacitor

even

when

the

clutch

is

engaged.

Being

also

designed

for

use

in

room-acoustical

measurements,

the

Beat

Fre-

quency

Oscillator

is

equipped

with

frequency

modulation,

for

which

a

re-

actance

tube

controlled

by

saw

-

tooth

oscillations

from

a

built-in

oscillator

is

switched

into

the

circuit

of

the

fixed

oscillator.

Both

the

frequency

and

the

amp-litude

of

the

saw-tooth

oscillation

are

adjustable

and

may

be

read

off

two

printed

dials.

Provision

is

also

made

for

external

modulation,

whereby

very

wide

limits

of

frequency

modulation

can

be

obtained.

By

means

of

a comp.!_essor

circuit,

which

~

can

be

controlled

from

an

~

~~t~ge,

it

is

possible

t~voltage,

current,

or

sound

pre

-

ssure

constant

during

measurements

when

using

the

oscillator

as

a

power

source.

5