BRUEL & KJAER 1022 - Automatic Power Regulation

BRUEL & KJAER 1022

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•

which

is

in

the

middle

of

the

range.

(

This

makes

certain

that

when

taking

a

recording

of

frequency

characteristics

,

where

the

lowest

attenuation

is

around

1ooo

c/s,

that

the

deflection

of

the

stylus

lies

within

the

scale

limits

of

the

paper

during

the

recording

).

Continuous

llecording

with

ten

Times

Enlarged

Paper

Speed.

The

following

method

is

adopted:

Set

the

"1 : 10

Synchronizing

Gear

Lever

"

in

its

inner

position

(released).

The

actual

paper

drive

speed

then

corresponds

to

the

large

numbers

marked

around

the

PAPER

SPEED

knob.

Recording

on

frequency

calibrated

paper

is

not

possible

in

this

position.

The

start

and

stop

of

the

recording

will

in

this

case

be

completely

controlled

by

means

of

the

PAPER

DRIVE

,

START

-STOP

toggle

switch.

F.

Automatic

Regulation

of

the

Output

Power.

By

means

of

the

compre

·

ssor

circuit

it

is

possible

to

regulate

the

output

from

the

oscillator.

When

a

constant

output

voltage

is

required,

the

output

voltage

from

the

Oscillator

is

used

as

a

control

voltage

. A

constant

current

is

obtain-

able

if

the

voltage

drop

across

a

resistor

connected

in

series

with

the

load,

is

used

as

the

control

voltage,

and

a

constant

sound

pressure

· is

maintainable

with

the

aid

of

a

regulating

1111icrophone.

The

microphone

is

then

placed

in

the

so~nd

field

fro11n

a

loudspeaker

which

is

driven

by

the

Oscillator,

and

the

microphone

output

voltage

used

as

control

voltage.

(It

is

essential

that

the

frequency

characteristic

of

the

microphone

is

linear

).

Proceed

as

follows:-

1.

Calibrate

the

Oscillator

as

de

·

scribed

under

Calibration,

see

under

A.

2.

Set

the

MATCHING

IMPEDANCE

switch

in

the

desired

position.

3.

Connect

the

load

to

LOAD

terminals

or

to

the

screened

output

socket

on

the

top

of

the

instrument,

see

B

or

C.

4.

Feed

the

control

voltage

to

the

COMPRESSOR

INPUT

terminal.

If

neces-

sary

use

an

amplifier

which

has

a

linear

frequency

characteristic

for

the

amplification

of

the

control

signal,

approximately

o.5

volt

being

required

for

full

utilization

of

the

compressor.

5.

Set

COMPRESSOR

VOLTAGE

and

OUTPUT

VOLTAGE

to

maximum

(fully

clockwise).

6.

Feed

the

voltage

to

be

measured

to

the

recording

instrument,

e.g.

the

Level

Recorder

Type

2305.

7.

Set

the

COMPRESSOR

SPEED

switch

in

one

of

the

positions:

30, 100,

300

or

1ooo

dB/sec.

8.

Regulate

the

desired

output

vollage

by

turning

COMPRESSOR

VOLTAGE

knob

counterclockwise.

Note:

When

the

Beat

Frequency

Oscillator

is

used

in

conjunction

with

the

Level

Recorder

Type

2305

the

writing

speed

of

the

Level

Recorder

should

be

kept

below

the

regulation

speed

of

the

compressor.

HI

•