Bruel & kjaer 1022 User guide

••

B & K INSTRUMENTS:

ACOUSTlCAL.

...

Condeoser

Microphone

s

Pi

ezo-E

lectric

Microphones

M

icrop

h

one

Pr

eamplifiers

Micro

pho

ne

Calibration

Equip.

Sound

Level

Meters

(general

purpose-precision-

and

impulse)

Standing

Wave

Apparatus

Tapping

Machines

Noise

Limit

Indicators

ELECTROACOUSTICAL.

.

..

Artificial

Ears

Artificial

Mouths

Artificia

l Masto

ids

Hearing

Aid

Test Boxes

Telephone

Measuring E

quipment

Audiometer

Calibrators

Audio

Reproduction

Te

st Equip.

STRAIN

....

Strain

Gauge

Appar

atus

Mu

ltipoi

nt

Panels

Automat

ic Sel

ec

t

ors

Balan

cing

Un

its

VIBRATION

....

Acceleromete

rs

Accelerometer

Preamplifiers

A

cc

elerometer

Calibrator

s

Vibration

Meters

Magnetic

Transducers

Capacitive

Tr

ansducers

Vibration

Exciter

Controls

Vibration

Programmer

s

Vib

ration

Signal

Selectors

Mini-Shakers

Complex

Modulu

s

Apparatus

Stroboscopes

GENERATING

....

Beat Fr

equency

Oscillators

Random

Noise

Gene

ra

tor

s

Sine-

Ran

dom

Generators

MEASURING

...

.

Measuring

Amp

l

ifiers

Voltmeters

Deviation

Bridges

Meg

ohmmeters

ANALYZING

....

Band-Pass

Filter

Sets

Frequency

Spectrometers

F

requency

Analyzers

Real-Time Analyzers

Slave Filters

P

sophometer

Filters

Statist

ica

l

Analyzers

RECORDING

....

Level

Recorder

s

(strip-chart

and polar)

Fr

equency

Response

Tracers

Tape

Recorders

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,

Beat Frequency Oscillator

Type 1022

A signal

generator

covering the

range

of

20-20,000 Hz and designed

especially

for acoustic and e·

lectro-

aco

ustic

measurements. Logarithmic

sweep and

automatic

drive for

recording

of

frequency

response

curves. The

output

s

igna

l can

be

frequency

modulated

and

controlled

by a

compressor

loop.

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CONTENTS

1.

INTRODUCTION.

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

..

5

2.

CONTROlS.

• . . . • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . .

..

6

3.

TECHNICAl

DESCRIPTION

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

..

........

10

4. OPERATION

..

.

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

"

..........

15

Preliminary Adjustments

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

.

..........

15

A. Calibration

..........

..

.

..

..........

.

..........

15

B.

Operation using

load

Termi

nals

.......

...

. . .

...

16

C.

Operation using Attenuator

Output

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

16

D.

Frequency Modulation

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

.

..........

16

E.

Automatic Regulation

of

Output

Power

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

17

F.

Automatic

Recording .

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

18

G.

Remote Controi

....

..

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

.

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

21

H.

Partial Blocking

of

Frequency

Range

. .

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

22

I.

Use

with

2020

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

.

..

........

. 24

5. APPLlCATIONS

..........

.

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

25

A. Electronic Measurements

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

.

.......

25

B.

Acoustical Measurements .

...........

...

. .

........

28

C.

Mechanical Measurements

...........

.

...........

.

41

6. ACCESSORI

ES

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

43

10:1

Gear

UG

3000

....

.....

. . .

......

.

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

43

Output

Transformers TU 0005 . . .

...

.....

...........

45

7. SPECIFICATIONS

.....•..............................

46

Dimensions:

Ext. dials and knobs Height

Type 1022 A 48 cm

19

inches

Type 1022 B 50.5 cm

20 inches

Type 1022 C 53.2 cm

21

inches

Accessories Supplied

1 Power Cord

1 Flexible Drive Shaft

UB

0041

1 Remote Controi

Plug

Jp 4722

3

Fuses

VF

0009

2

Scale

lamps

VS

1271

2

Scale

lamps

VS 1273

Width

38

cm

15

inches

40 cm

16

inches

48.2 cm

19

inches

Depth Weight

20

cm

15

kg

8 inches 331bs

27.3 cm

19

kg

11

inches 421b$

20.5 cm 19

kg

8 inches 421bs

49

Accuracy

of

Attenuators

Over full

frequency

range

2%

Power Requirements

Mains supplies

of

100-115-127-150-220-240

Volts AC and

50

to

400

Hz.

Power

consumption:

Without

load

With

2.5

W load

20

Watt

26

Watt

Cabinets:

With

the

mechanical design

of

all B &

Kapparatus,

it

is

very easy

to

interchange

the

instruments

with

the

various cabinets.

The

instruments

are

delivered

in

metal cases as

standard

fittings which can be

mounted

in

any

desired way i.e. -mahogany

cabinet

or

frame

for

19"

standard

rack.

Type

1022A

The

B.F.O.

is

in

a metal case.

Type

10228

Similar

to

Type

1022A

but

the

instrument

and

the

metal case are housed

in a mahogany

cabinet

with cover.

In

this

cabinet

it

is

easy

to

transport

the

instrument.

Type

1022C

Similar

to

Type

1022A,

but

it

is

supplied in a frame ready for

mounting

the

instrument

in

a

19"

standard rack.

The

instrument

is

delivered

together

with a chain wheel which can be

coupled

with

the

chain drive supplied with

2305

C.

(The Level Recorder used

for

19"

standard

rack mounting).

1.

INTRODUCTlON

The

Beat

Frequency

Oscillator

Type

1022

is

a precision signal

generator

using solid

state

circuitry

throughout.

It covers

the

range

20-20,000

Hz

and

is

designed

for

acoustical, vibrational

and

electrical measurements.

The

1022

works

on

the

heterodyne

principle using

two

high

frequency

oscillators

one

of

which

operates

at

a fixed

frequency

while

the

frequency

of

the

other

can be varied.

The

required audio

frequency

is

then

obtained

by

mixing

these

frequencies

to

produce

a

beat

frequency.

The

instrument

contains

several features

that

aid experimental work. A

regulator stage

is

provided so

that

for instance

constant

sound

pressure

or

vibration level may be maintained.

The

output

signal can be

automatically

frequency

modulated

by

an inter·

nal

generator

to

produce

a warble

tone

for use during reverberation mea·

surements.

Alternatively

the

output

signal can be

externally

modulated

to

allow wider choice

of

modulation

frequency

and

frequency

deviation.

The

output

attenuator

has a range

of

100

dB

in

10 dB steps and

the

output

impedance can

be

varied

to

give

maximum

power

(2.5

W)

in a load

of

6·60-600

or

6000n.

The

1022

may be

swept

continuously

through

its

frequency

range

by

means

of

an

externa

I

motor

drive. Alternately, parts

of

the

frequency

range

may

be

blocked with adjustable cams

to

suit

any

particular sweep program.

If

it

is

driven

by

the

Level Recorder

2305

it can also be

automatically

synchronized

with

frequency

calibrated paper.

Outputs

of

100-120

kHz variable

and

120

kHz fixed frequencies are

available

for

use

as

controi

frequencies for

the

Heterodyne

Slave Filter

2020.

Remote

controi

facilities are provided

to

start

and

stop

the

scanning

and

the

oscillator and

for

instance

to

lift

the

pen

on

the

Level Recorder

when

the

oscillator

is

sweeping

outside

the

frequency

range

of

interest.

48

5

2.

, CONTROLS

r

------~---------..

Att

enuotor

s.---

Ou

t

pu

t

P

ow

er

Powe

r

Fre'1uency M

atc

hing

Se

at

Automat

ic

Scanning

F

re'1

uency

In

cre

ment e

,.1

___._

Compressor

I

nput

Modulation

Out

pu

t

Fr

e'1

uency Level

~

({

)

;

~'

~

10

00Hz

R

ef

. Signal

Fre'1

ue

nc

y

Co

mp

re

ssor

Sc

ale

Sp

e

ed

Alig

nment

Fig.2.

1.

Front

Panel

FRONT

PANEL

POWER: On/

off

switch for mains supply.

POWER

FREQUENCY

BEAT:

Pushbutton.

When depressed

and

held

in, a

beat

between

the

power

supply

fre-

quency

and

the

output

frequency

of

the

B.F.O. can be

observed

on

the

meter.

Ry

th

15

mE'~'!5

thE'

outp'.!t frequency can

be cal ibrated

with

the

main

frequency

scale.

Frequency

Modulation

Internal: Variable in steps,

1-1.6-2

.5-

4-6.3-10-16

-25

Hz.

Oscillator

Stop

By silent

push-button

or

by

remote

controI.

Attenuator

Output

Ma

ximum

Output

Voltage

12

V

Load

Output

Maximum Pöwer

Output

2.5W

Minimum permissible load impe-

dances are

marked

at

the

Matching

I

mpedance

switch positions.

They

are:

6n

60 n

600 n

6000 n

120 kHz

and

100-120

kHz

Outputs

Output

Level

approx.

200 mV

Output

Impedance

100 n

Compressor

Input

Impedance

approx

. 25 kn

Maximum

input

level 50 V

Remote

Controi

Socket

For

th

e r

equ

ire

ment

s of this sock

et

, see R

emo

te

C

on

tro

l,

Operation

ch

ap

-

ter.

6

47

7. SPECIFICATIONS

Frequency

Range

20-20.000

Hz.

Frequency

Sca

les

Main Scale: Logarithmic over 3

decades.

Incremental

Scale

:

Range

of

-50

to

+ 50 Hz

of

main

scale

setting.

Frequency Characteristics

(without

compressor loop)

Attenuator

Output:

Better than ±0.3 dB

Load

Output

(with 1

watt

load): Better than ±0.5 dB

Distortion

Frequency

Hz

20 200 2000 20,000

Attenuator

Output

(rv

lOV

output)

0.2% 0.1%

0.1

% 0.2%

Load

Output

(1

watt

load) 0.3% 0.15% 0.15% 0.4%

Automatic

Output

Regulation

The built-in compressor amplifier maintains regulation up

to

55

dB

and

will

maintain a constant voltage, current

or

sound pressure level

to

with

in 1.5 dB

over

the

whole frequency

range.

Linearity

of

the frequency characteristic

is

better than ±0.3 dB.

Regulation

speed

variable in steps:

30-100-300-1000

dB/see.

Frequency Deviation

Internal: Variable in

steps,

O± 10 ± 16 ± 25

±40

± 63 ± 100 ± 160

±250 Hz

Externai: With externai generator continuously variable

from

O

to

±300 Hz. Maximum Modulation Sensitivity 5

mV

/Hz

(at 250 Hz frequency

deviation).

AUTOMATIC

SCANNING:

FREOUENCYINCREMENT:

OSCILLATOR

STOP:

MODULATION

FREOUENCY:

REMOTE CONTROL:

FREOUENCY

DEVIATION:

COMPRESSOR SPEED:

FREOUENCY SCALE

ALlGNMENT:

1000 Hz

REF.SIGNAL:

OUTPUT

LEVE

L:

Connects the variable capacitor

of

the

B.F.O.

to

a

worm

drive which

can

be

connected

to

and

driven

by

an

externaI

motor.

Allows exact variation

of

the

output

fre-

quency

within

-50

to

+50

Hz

of

that

indicated

by

the main frequency

scale.

Pushbutton

to

interrupt

the oscillator.

It

is

fitted

for

reverberation measure-

ments and

is

noiseless.

Selects frequency

of

modulation. Choi-

ce

of

1-1.6-2.5-4-6.3-10-16-25

Hz

or

externai modulation.

Six-pin socket

for

connection

of

various

forms

of

remote controi and externai

frequency modulation. For connections

see

Operation chapter paragraph

G.

Modulates the frequency

of

the

fixed

oscillator and hence the

output

frequen-

cy

by O

to

±250 Hz.

Selects the

time

constant in the regula-

tion

circuit. Gives regulation

speeds

of

30-100-300-1000

dB/see.

Fine and

Coarse

potentiometers

to

ad-

just

the

output

frequency

to

coincide

with

that

indicated on

the

main

scale.

When this

button

is

depressed and the

main frequency

scale

is

set

to

"1000

Hz,

Ref.Signal"

an

output

reference signal

is

produced.

Potentiometer giving continuous adjust-

ment

of

output

signal when the com-

pressor

circuit

is

not

in operation.

46 7

COMPRESSOR INPUT:

COMPRESSOR

VOLTAGE

:

LOAD:

MATCHING IMPEDANCE:

ATTENUATOR:

ATTENUATOR

OUTPUT:

MECHANICAL

DRIVE

CONNECTION:

For

connection

of

the

signal

from

the

regulating

transducer

when

automatic

regulation

of

the

B.

F.O.

output

is

re-

quired.

Input

impedance

25

kU

Maxi-

mum

range

of

regulation 50 dB.

Logarithmic

potentiometer

for

controi

of

the

output

voltage

of

the

instrument,

when

compressor

loop

is

applied.

Output

terminals

of

variable

output

im-

pedance.

Contro"ed

by

Matching Im-

pedance

knob.

The

right-hand

terminal

is

grounded.

6-60-600-6000D

indicates

the

mini-

mum

load

impedance

for

each

switch

position.

Another

position

feeds

the

output

through

the

Attenuator.

When

"Matching

Impedance"

is

set

to

"Att"

the

output

signal

can

be

attenuat-

ed

in

ten

accurate

steps

of

10 dB.

The

other

values

indicated

by

the

knob

posi-

tions

refer

to

the

RMS voltage (mV)

available

at

full scale

meter

deflection.

Output

signal fed

through

this

socket

when

"Matching

Impedance"

set

to

"Att"

.

Agrounding

socket

is

placed be-

side it.

Located

on

both

sides

of

the

instrument

are

sockets

for

the

connection

of

an

ex-

ternal

mechanical drive

for

automatic

frequency

sweep.

The

shaft

connection

fits

the

Flexible Drive

Shaft

UB

0041

which

forms

the

mechanical link be-

tvV6eii the B.F.O.

and

the

Level

Recor-

der

2305.

OUTPUT

TRANSFORMER

TU

0005

This

transformer

is

designed

to

a"ow

symmetrical

output

from

the

atten-

uator

output

of

the

B.

F

.0

. 1022.

(Symmetry

better

than

0.1

%1.

The

out-

put

impedance

is

600D

and

the

distortion

0.5%

at

20

Hz

with

maximum

output

voltage

from

the

B.F.O. (12.5

V)

.

The

accuracy

of

the

Transformer

is

±0.2

dB

in

the

frequency

range 10 Hz

to

35 kHz.

In

addition

a

core

material has been

chosen

for

the

transformer,

which

makes it possible

to

"preload"

the

secondary

winding

with

a

current

of

100

mA

without

causing

additional

distortion

for

frequencies

above

300 Hz.

The

transformer

ratio

is

\ffQT.'"'

The

voltage transmission loss

of

the

transformer

when

loaded

by

600D

is

approximately

16 dB.

8 45

Note: For correct synchronization

of

paper and sweep speed

the

syn·

chronizing Gear Lever X

on

the

2305

(Fig.6.

2.1

should be

in

its

outer

position and

the

knobs PAPER SPEED and DRIVE

SHAFT

SPEED should

be set as

in

TABLE I

PAPER SPEED . DRIVE SHAFT SPEED

mm/see. rpm.

0.0003

0.036

0.001

0.12

0.003

0.36

0.01 1-2

0.03

3.6

0.1

12

0.3

36

1.0

120

TABLE I

Drive

Sheft

II

1022

or

1024

~

o

e

.

~

... ;.

,

"".

;

~

.

~~.:.

~

-

...

Level

Recorder

10:1

Geer

2305

..

,:~

~

f

:

UG~

.

-.-

e"

'

~

.-.

~~

~

.

=

~

=~

~~

-

~.

~

·~

OOlft

II :.--

,.

e:."

.:T

.'

,.

--

..

0:.·..,

h,:

.

'

,,~,

•

....

~

.:.

--

_

.-

-

120

kHz

100-120kHz

To

Sleve

Filter

2020

-170107

Fig.6.2. Connection

of

Gear UG

3000

REAR PANEL

100

-

120

kHz AND

120

kHz: These sockets supply controi voltages

for use with

the

Heterodyne Slave Filter

2020. The

output

impedances are

100n

and

output

levels approximately

200

mV.

44 9

3.

TECHNICAL

DESCRIPTION

A block diagram

of

the

1022

is

shown in Fig.3.1.

L

ood

OUTPUT

Ert

.

120~Hl

Mod.

Output

'n

pv,

Aue'''JoIO{

(ontro(

R.mot.

O".IPUI

Input

I"

..

"J

'

Fig.3.1. Block Diagram

The

fixed oscillator

is

atuned

LC

type

and

works

at

120

kHz. Incorporat-

ed

in

the

tuned

circuit

is

a variable

capacitor

which

is

operated

by

the

Frequency

Increment

knob.

This

allows

exact

frequency selection within

±

50

Hz

about

any setting

on

the

main scale.

In

addition

this capacitor per-

mits frequencies

down

to

10

Hz

to

be

obtained

at

the

risk of slightly more

distortion.

An

output

to

supply a reference signal

or

a

controi

signal for

the

Hetero-

dyn

e Slave Filter

2020

is

provided.

The

output

impedance of

the

120

kHz

output

socket

is

1

oon

and

the

signailevei

is

of

the

order

of

200

mV.

The

fixed oscillator can be frequency

modulated

to

produce

a warble

tone.

The

oscillator

is

connected

directly

to

a reactance circuit

to

enable

~x

ternal

modulati

on

of

the

s

ig

na!, b

ut

in

the

case

of

in

te

r

iiu!

mod

ul

at

ion a

relaxation

type

of oscillator employing a unijunction transistor

to

controi

the

reactance circuit

is

also used.

6. ACCESSORIES

10:1 GEAR

UG

3000

When making narrow band frequency analyses of a spectrum

that

has

narrow resonances it

is

important

to

have a slow and

constant

sweep speed.

Clearly

if

the

sweep speed varied,

the

narrow filter might

jump

past

one

of

the

resonances.

The

2020

is

driven electrically from

the

1022

which

is

in

turn

driven by a

flexible

shaft

from

the

Level

Recorder 2305. Hence for narrow band ana-

lyses

the

10:1 Gear

UG

3000

is

recommended (Fig.6.1.l. Generators

1022

or

1024

connect

directly

to

this gear, which

is

driven from DRIVE

SHAFT

II

of

the

2305

Level Recorder via

the

Flexible Shaft

UB

0041,

as shown in

Fig.6.2.

Thus

the

mechanical loading

on

the

Flexible

Shaft

is

considerably

reduced and

the

sweep speed regulation

is

improved by a factor

of

10

or

more.

To

1022

or

1024

To

UB

004i

Fig.6.1.

The

10:1

Gear

UG

3000

43

10

To

measure

the

strain

on

the

test

object

a resistance strain gage should be

used and a Strain Gage

Apparatus

1516

will be

found

ideal as

the

measuring

bridge. The

output

voltage from

the

Strain Gage Apparatus can be fed

directly

to

a Level Recorder with linear

potentiometer

for

automatic

record-

ing.

An example

of

such a recording,

taken

on

a

thin

metaI bar, showing

the

mechanical strain and indicating its resonant frequency,

is

shown

in

Fig

.

5.21.

DDDDDDOOOODDODODDDDDDDODDDJ

50

db

20

10

o

50

100

200

Hz

300

~o

1?DD

I{q

Fig.5.21. Recording

of

mechanical strain in a

bar.

Instrumentation set-up

as

in Fig.5.20.

The

reactance circuit

is

needed

to

controi

the

actual frequency deviation

(modulation swing)

of

the

fixed oscillator by producing an inductive react-

ance across

the

oscillator's

tuned

collector. The deviation can be varied

linearly from O

to

±

250

Hz

where

the

sensitivity

is

approximately

5 mV/Hz.

A

saw·tooth

generator determines

the

frequency

of

modulation i.e.

the

rate

of

change

of

the

frequency swing

of

the

oscillator. Frequencies

of

1-1.6-2.5-4-6.3-10-16-25

Hz

are available. Provision

is

also made

for

modulation by an external generator. Alternative modulation frequencies

or

wave shapes can

the

n be chosen and frequency swings

of

up

to

±

300

Hz

obtained

(but

the

modulation sensitivity varies).

The

signal

from

the

fixed oscillator

is

passed

to

aregulating

amplifier

which controls

the

output

level.

The

regulating amplifier

is

used

to

perform

the

oscillator

stop

and dead zone blocking. A compressor amplifier can

be

switched

in

to

controi

the

regulating amplifier so

that

constant

output

level

is

obtained.

When

the

instrument

is

being used for instance

to

power a

loudspeaker,

the

compressor circuit can be used with a

microphone

to

main-

tain a

constant

sound pressure level.

The

compressor circuit consists

of

an amplifying stage and a full-wave

averaging rectifier stage.

The

signal from

the

rectifying stage

is

then

used

to

varv

the

gain

of

the

regulating amplifier. A variable

potentiometer

(Com-

pressor Voltage)

in

the

input

circuit

of

the

regulating amplifier

can

be used

to

controi

the

output

power from

the

instrument

when

automatic

regula-

tion

is

used.

The

speed with which

the

variation

in

output

level

is

regulated

back

to

normal

depends

on

the

setting

of

the

Compressor Speed knob,

but

also

depends

to

a certain

extent

on

the

amount

of

the

deviation from

the

normal

level. Compressor speeds

of

30

-

100

-

300

-

1000

dB/sec. are available

and are

determined

by

the

integration time

constant

of

the

rectifying cir-

cuit.

The

input

impedance

of

the

Compressor Input

is

approximately

25

kQ

and

the

maximum

range

of

regulation

is

50

dB. Regulation characteristics

for

different

positions

of

the

Output

Level

potentiometer

are shown

in

Fig.3.2.

The

variable oscillator

is

of

similar design

to

the

fixed

one

except

that

it

has a variable capacitor

in

its

tuned

circuit

to

varv

the

oscillation

frequency

between

100

and

120

kHz. A worm gear,

connected

to

the

capacitor

42

11

• dB

Output

L.v.l

10

Distorled

Signal

MAX.

METER

DEFLECTION

-10

-20

-30

Output

LeveL

- o }

~~10

dB

dB down from

~30

dB

max~

meter

-40

50

dB

~

deftection

-50

-60

-70

_Naise

LeveL

of

B.F.O.

-80

,--,:'-::::='-~====

]

-90

-20

-12

-6

-3

---t--~----~------~----~----------~--.~

dBre

1Y

..

y

0~1

0.2

0.3

0.4

0.5

0~6

0.7

0.8

0~9

Camp~

Voltage

on

"Compressor

Input"

CCompressor Voltage"'

on

maximum)

17oo})1j

Fig.3.2. Regu!ation characteristics

for

different

positions

of

Output

Leve!

potentiometer

spindie, perrnits

automatic

tuning

with

the

aid

of

an externai

motor

such

as

that

of

the

Level Recorder 2305. A rnagneiic ci

utc

h, which can be

remoteiy

controlled,

is

used

for

connection

of

the

externai drive

to

the

capacitor

spindie.

C. MECHANICAL MEASUREMENTS

Strain Measurements

on

Vibrated Objects

In

the

measuring

of

mechanical strain

on

objects

under

vibration, it

is

essentiai

that

the

vibration acceleration

is

kept

constant

within

the

range

of

frequencies

at

which measurements are being

taken

and

that

inherent

re-

sonances in

the

system have no

effect

on

the

magnitude

of

the

driving force.

The

illustration

in

Fig.5.20. shows a

test

rig

for

strain measurements

of

small mechanical

constructions,

the

B.F.O.

1022

section

of

the

Automatic

Frequency

Response Recorder

Type

3308

feeding

the

shaker,

the

object

under

test

being placed

on

the

shaker

table.

2623

smaLL

(;lo mechanicaL

•

I~I

,j

:

-.

:"j:

construc-

tion

·e"-'"'0

\

..

•

~

J

'.

-

~

o

....

;:i

!;

:

·!·.:!._

~

Ern

!

.

l2-

~

•

3308

17""

'If

Fig.5.20.

Set-up

for

the measurement

of

vibration in small specimens.

To

keep

the

acceleration

constant

a controlling system

is

utilized. This

system consists

of

an Accelerometer

mounted

on

top

of

the

test

object. As

the

acceleration has

to

be

constant

and

under

controi

the

output

voltage

is

connected

via a Preamplifier

2623

and

a Measuring Amplifier

2606

to

the

compressor

input

of

the

B.F.O.

By using

the

Measuring Amplifier

2606

the

acceleration can be read

directly, so

the

force

on

the

test

object

can be calculated knowing

itsmass.

12

41

le-veIRe-corde-r

2305

M,

oll"';"

; Amp

löf

l. t

260

6

M

eo~u

.

i

ng

Amp

li

fi• •

2606

BF

O

102 2

ffi

(

~

:

510"fI

Filler

..

.;;.

:

i'

202

0

r~

i

.

~-

.

-

~

,

-'.... _ a

~

_

.~

:

:i

!~,'!

i!

:.

'.

' .

, F

1

00-

1

20

kHI

12

01c

Hl

Fig.5.

19.

Set-up

for

automatic

recording

of

hearing

aid

harmonies

The

percentage

harmonic

distortion

can

now

be calculated

and

ios defined

by:

Pr

-x

100

%

P

Where

"Pr"

is

the

RMS

harmonic

sound

pressure level excluding funda-

mental

and

"P"

is

the

overall RMS

sound

pressure level.

Alternatively

this

can be expressed by:

(P22 +

P3

2 +

P4

2 x

100

%

·

-----

-t

Harmonic Distortion =

~12

+ P 2 +

P3

2

where P1 =

amplitude

of

fundamental

sound

pressure

Pn

=

amplitude

of

the

n

th

harmonic.

Note: When

the

"Rejection"

output

is

used

for

harmonic

analysis

the

compressor feedback voltage can be

taken

from

the

"Output"

of

the

same

instrument,

since

both

"Rejection"

and

"Output"

circuits

function

simul-

taneously.

When

the

capacitor

is

set

to

frequencies above

20

kHz

or

below

20

Hz

the

signal from

the

fixed oscillator

is

blocked so

that

no

output

voltage

is

obtained.

This has

the

advantage

that

when

automatic

recordings are being

taken

with

the

Level Recorder

2305,

no

unwanted

curves

appear

on

the

paper.

The

cut-off

section can be made wider by means

of

the

adjustable

cams fixed

on

the

capacitor

spindie (Fig.4.5).

The

Remote

Controi plug

is

also needed

to

make

certain

connections

inside

the

instrument.

By

this

method

the

overall frequency range

of

the

apparatus

can be reduced

to

about

one

octave. In applications where

the

1022

is

used

with

the

Level

Recorder

2305

the

adjustable cams can be made

to

operate

the

pen

lift

..

A

1000

Hz

reference signal can be supplied

at

the

output

sockets

when

the

Reference Oscillator

is

connected

and

the

scale

pointer

is

set

to

the

position

1000

Hz

Ref.signal.

The

use

of

this reference signal can be seen in

the

operation

chapter.

The

signals from

the

fixed and variable oscillators are mixed and

then

passed

to

a low-pass filter.

The

filter has a cut-off

frequency

of

50

kHz

and

is

used primarily

to

eliminate

any

100

-

120

kHz

or

220

-

240

kHz

compo-

nents.

The

filtered signal

is

then

fed

to

the

output

amplifier. This will give

an

output

power

of

2.5

W nominal load (Le.

the

load indicated on

the

Match-

ing

I

mpedance

switch).

The

output

ampl ifier

is

current

limited

to

protect

the

transistors.

Finally

the

output

signal

is

fed

to

an

auto

transformer

for

impedance

matching with

the

load.

The

markings

6-60-600-6000D.

around

the

Matching Impedance Switch indicate

the

minimum

load impedances

that

should be used for each switch position.

The

signal

can

also be passed

to

an

output

attenuator

which allows

output

signals

to

be selected

between

120

pV

and 12 V, (full scale

deflectionl,

in

accurate

10

dB

steps.

The

over-

all

accuracy

of

the

attenuators

is

2%.

The

voltage at

the

output

terminals

is

indicated

by

a

transistor

voltmeter

which measures

the

average value. It

is

calibrated

in

RMS

values

of

a sinusoidal voltage and

the

accuracy over

the

frequency

range

20-20,000

Hz

is

1.5%

at

full scale deflection.

Additionally

,

there

is

a dB sca

le

which gives dB values

re

1 volt.

It

should be

noted

that

when

the

Attenuator

Output

is

used,

the

output

voltage

only

equals

the

corresponding

meter

deflection

when

the

impedance

of

the

load

connected

to

the

terminal

is

high

compared

with

the

50D.

attenuator

impedance.

The

sensitivity

of

the

voltmeter

is

automatically

changed

when

the

posi-

tion

of

the

Matching

Impedance

switch

is

altered. Full scale

meter

deflec-

tion

in volts

is

indicated

for

each switch position.

The

Attenuator

switch

is

similarly marked

and

in

addition

has dB values re 1 volt.

40

13

The

signal-to-noise ratio

of

the

instrument

is

better

than

70

dB

for

maxi-

mum

output

voltage. It

is

independent

of

the

position

of

the

attenuator,

but

somewhat

dependent

on

the

position

of

the

Output

Level

potentiometer.

The

optimum

setting

is

when

the

voltmeter

indicates

20

dB.

The

amount

of

harmonic distortion also

depends

on

the

setting

of

the

Output

Level

potentiometer.

As

long as

the

output

is

kept within

the

meter

range

the

distortion

will be

of

the

order

indicated

in

Fig.3.3.

The

1022

can be operated

from

100,

115,

127,150,

220,240VoltsAC

and

50

to

400

Hz mains supplies and

the

maximum power

consumption

is

of

the

order

of

26

Wwith full load.

O·L l

Watt

La

a d

fa3

/

z

c "

'"

1'-..

V

~

0·2

.........

2 V V

~

i'-

r--

V

o

t--

l..--At"t.

la

v

Na

lo

a d

:;

o·,

r--

t---

-

I----

u

c

l

c

o

Z

10

20

3o 50 laO l k lOk

20k

Frequency

( Hz) _

1700

JS

Fig.3.

3.

Distortion curves

for

different loads

D D D D D D D D D D D D D D D O D D D D D D D D D D O D D D [

e'

Q

~

j

CII'

~

50 25

B.Gel&

(!Gr

-Objott

-

--

db db

Sound

tran

sm

ission

.,

'"

recording

wIthout

Filtering

JO

"

...

"'-

'"

10

0-

,

"""

RICI

~

z-,

L..r

~

L l

.....

F

r

~

20

10

,

p

""

'W

r.

So.,:

p

....

Sp..:

50

e

o.,

MuhfpIy

Fnq.

Sco&.

b

r;

_'

_ o 0 -50

100

200

"'"

1000 2000

>XXI

1

00

1lO1lO

OP1123

100

1000 10(

00

16'3S.5"

Fig.5.18. Sound transmission recording

without

filtering

An

instrument

set up

for

the

automatic

recording

of

hearing aid harmo-

nics

is

shown

in

Fig.5.19.

The

test

environment

is

provided by

the

Type

4212

Hearing Aid Test

Box, which gives practically free-field

conditions

over

the

frequency range

150

Hz

to

5 kHz.

The

receiver

of

the

hearing aid

under

test

is

excited by a

loudspeaker inside

the

anechoic

chamber

of

the

test

box.

Sound

pressure

at

the

position

of

the

receiver

is

maintained

constant

byaregulating

condenser

mi

crophone

which provides feedback

to

the

compressor circuit

of

the

oscil-

lator supplying

the

loudspeaker signal.

The

hearing aid

output

is

coupled

to

an artificial ear as required by

the

I

EC

(Recommendation

118).

The

artifi-

cial ear contains a pressure response

microphone

which

detects

the

output

from

the

earphone. Using

the

Slave Filters

"Output"

(L.F.) and

"Rejection"

out

p

ut

s the respective frequency and har

monie

analys

is

spectrogr

<lms

can be

recorded on

the

same

frequency

calibrated

chart

using

the

Level Recorder.

14

39

[ooooooooooooooooooooooooooooooJ

Br

O.1

& KjCllr

....

BnW"

klc-

-"''''

_ot;o<t-

__

.....

Sound

transmission

anal;tsis

'"

uSlng

2020

Slcve

Filter

3.16Hz

Bandwidth

'"

"

'"

10

'"

"-

""'

"'"'

"""

RMS

z-t-

,

10

5

LlJ&

Fr

.:

20

,,.

50

'r

h.

Sp

. e

0.1

.......

,

'-

""'"

.,,

_1_

••

.....

~

200

....

'00

'000

2000

",..

'OX

OP

1123

'"

100

"'"

1000

10C

00

16f35~

Fig.5.

17. Sound transmission analysis using a Heterodyne

Slave Filter

2020

with 3.15 Hz bandwidth

Experimental results

obtained

for

a receiving

room

where a high level

of

background noise was

present

are

shown

in

Fig.5.17.

and

5.18.

The

results

obtained

using

the

2020

(Fig.5.17.)

show

a considerable

improvement

in

signal

to

noise

compared

to

those

obtained

with no filter (Fig.5.18.).

Note:

To

ensure

that

the

compressor

circuit

is

controlled

from

the

funda-

mental

of

the

sound

source,

another

2020

could

be

used with

the

2606

in

the

compressor loop.

Automatic

Recording

of

Harmonics in Hearing Aids

Another

use

of

the

Heterodyne

Slave Filter with

the

1022

is

shown

below.

The

2020

can be used

for

frequency

rejection

whereby

it

will reject

frequencies

by

over

40

dB over a

3.15

Hz

bandwidth.

38

4.

OPERATION

PRELlMINARY

ADJUSTMENTS

Before

the

instrument

is

used check

the

voltage

selector

on

the

rear panel

is

set

to

the

correct

line voltage. If not, remove

the

central fuse

and

adjust

with a small coin

or

screwdriver.

A.

CALlBRATION

1.

Switch

on

and

allow 1

minute

to

warm

up.

2.

Set

MODULATION

FREOUENCY

and

COMPRESSOR SPEED

to

"Off".

3.

Set

main scale

pointer

to

the

frequency

of

the

mains

supply

(e.g.

50

or

60

Hz) checking

that

the

frequency

increment

scale

is

set

to

zero.

4.

Set

the

meter

deflection

to

higher

than

centre

sca

le

reading with OUT-

PUT LEVEL knob.

5. Press POWER FREOUENCY BEAT

button

and

hold

"in".

At

the

same

time

slowly

adjust

the

FREOUENCY

SCALE

ALlGNMENT

FINE

knob

until a large

fluctuation

registers, slows up,

and

practically ceases

on

the

meter

dia!.

6.

Set

main scale

pointer

to

20

Hz and

subtract

20

Hz

with

FREOUENCY

INCREMENT knob.

If

the

meter

deflection

dropsto

zero

then

the

B.F.O.

is

·calibrated. If

not,

continue

to

point

7.

If

the

meter

deflection

does

not

drop

to

zero,

adjust

FREOUENCY

SCA-

LE

ALIGNMENT COARSE with a screwdriver until

the

meter

deflection

does.

8. Reset

the

main scale

po

i

nter

to

the

frequency

of

the

mains

supply.

Reset

frequency

increment

scale

to

zero. Make a final

adjustment

with FRE-

OUENCY SCALE

ALlGNMENT

FINE

to

obtain

the

exact

position

of

"slow

beat"

as in

point

5.

The

B.F.O.

isthen

calibrated.

15

B.

OPERATION USING

LOAD

TERMINALS

1.

Set up and calibrate

the

Oscillator as above

in

A.

2.

Select suitable matching impedance for the load using

MATCHI

NG

IMPE-

DANCE switch.

3. Connect load

to

LOAD

terminals.

4. Turn pointer on main frequency dial

to

desired frequency, finely adjust-

ing with FREOUENCY INCREMENT knob

if

necessary.

5. Select required

output

voltage using OUTPUT LEVEL knob.

C.

OPERATION USING ATTENUATOR OUTPUT

1.

Set up and calibrate

the

Oscillator

as

above

in

A.

2.

Set MATCHING IMPEDANCE switch

to

"Att".

3. Select appropriate voltage range with ATTENUATOR knob.

4. Connect load

to

ATTENUATOR OUTPUT.

5. Turn pointer on main frequency dial

to

desired frequency, finely adjust-

ing with FREOUENCY INCREMENT knob

if

necessary.

6.

Select required

output

voltage using OUTPUT LEVEL knob.

Note: The meter reading

is

correct only when the impedance of

the

load

is

high compared

to

the

50,Q attenuator impedance.

D. FREQUENCY MODULATION

When a frequency modulated

output

signal

is

required:

1.

Set

knobs:

MODULATION FREOUENCY required value

FREOUENCY DEVIATION zero

2.

Calibrate

the

Oscillator from point

A.

3. above.

3. Set FREOUENCY DEVIATION knob

to

required bandwidth.

:0

o D C O O O D C Q O O O

[J

O D O D D O O O O D O O O D O O O C O O O O

Cl

O O O D O O

CI

O O O O D O O

"'

~

Goto+

L

I.-

ho

_ .

........

_

~

---

-

.....

,.

_

.

~

-

....

__

.

"-_.

-

~

ap

0123

m

1000

10000

Fig.5.15. Reading obtained

with

a set-up

as

in

Fig. 5.14.

50

dB

range

potentiometer

used

in

Leve/ Recorder

A set up

is

shown

in

Fig.5.16. where a compressor loop

is

used

to

keep

the

sound level constant. The feedback signal

is

amplified by a Measuring

Amplifier 2606. Another 2606

is

used

in

conjunction with

the

2020

to

analyze

the

attenuated signal

in

the

receiving room. The analyzed signal

is

then recorded on frequency calibrated paper using a

Level

Recorder 2305

and thus provides a direct measure of

the

sound insulation qualities

of

the

room

at

any frequency

in

the

measuring range.

S

our(

e R

O(lm

Re

, . ;

...

ln9 R(lem l

ev

el Re

(ord

. r

2305

Micro

p

hon

e

414

5

1

02

2

@o

•

I

~

I

,

~

:

51

0ve

Fi

ll

er

:.

-.

2020

ii

r~

:i

~

HI

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

~

-.

w

..

.- •

;

_

i:~

~

'

!

-

.

:

!

_

.

~

....----.,

I •

1

00

-1

2

0kH:t

12 0

kH

z:

170

Q

1.{7

Fig.5.16. Set-up

for

measurement

of

airborne sound insu/ation

using a Heterodyne

S/ave

F

i/ter

2020

37

16

receiver room transmi

tter

room

414

5 4145

L

.

S

·

'~1+t-1I

--,

261

9 2619

- -

=1=1

_:.

!:

r-

@o

44

08 ·

.

~

."-',

·

~

.

;

i

~

:

e:

-

.-

e

:'

....

···

\

.,

'

;

:

~

I '1

•

\

~

i

.

..

""7'"

ift

:

.

i

!

~

:

'

!

·

'

:;

~

.

-,-

'

.

'

.

~

I'

lIP

t!!

:~

4Tl

@

~

-:,~

,

~

--

-----u>O6 [m' 3

30

8

..

1

11oo'lb

Fig.5.14. Set-up for measurement

of

the sound insu/ation

properties

of

a wall

ing Amplifier

2606,

the

different

sound

leve

Is

picked up

in

the

two

rooms

are taken alternately and ampl ified before being fed

to

the

Level

Recorder.

The

result

is

that

two

independent curves are automatically reproduced

on

the

recording paper, enabling

the

sound level difference between

the

two

sides

of

the

wall

to

be read off

in

decibels. Such a recording

is

shown

in

Fig.5.15. The sound absorbed by

the

receiving room must be taken into

account

.

The

main problems

in

the

transmission and reception

of

airborne sound

are

the

power

aV;Jilable

from

the

source and

the

signal

to

noise ratio

of

the

receiver. Both these problems can be eased

if

a narrow band noise source

and a narrow band receiver are used.

The Heterodyne Slave Filter

2020

has very narrow bandwidths

and

is

ideal for such measurements. It can also be directly controlled by

the

1022.

4. Proceed from

point

B.

20r

C.

2 as required.

E.

AUTOMATIC REGULATION OF OUTPUT POWER

By

means

of

the

compressor circuit it

is

possible

to

regulate

the

output

from

the

oscillator. When a

constant

voltage

is

required,

the

output

voltage

from

the

oscillator should be used as a controi voltage. (Fig.4.1a.l. A con-

stant

current

is

obtainable

if

the

voltage

drop

across a resistor

in

series with

the

load

is

used as

the

controi voltage (Fig.4.1 b.l.

Similarlya

reference

microphone can be used

to

controi sound pressure

or

an accelerometer can

be used

to

controi vibration level. Examples can be seen

in

the

Applications

chapter.

Lood

__

o ,

_0---

-'

From

Oscillator

To

Compressor

To

Compressor

Input

o)

Constant

Voltoge

b)

Constant

Current

1700%

FigA.

1.

Constant vo/tage and constant current compressor

/oops

To use

the

compressor loop proceed as follows:

1.

Set up

and

calibrate

the

Oscillator as described above in

A.

2.

Set

the

MATCHING IMPEDANCE switch

to

the

desired position.

3. Connect

the

load

to

LOAD terminals

or

to

the

ATTENUATOR OUTPUT

at

the

top

of

the

instrument, see B

or

C.

4. Feed

the

controi voltage

to

the

COMPRESSOR INPUT terminal.

If

neces-

sarv use an amplifier which has a linear frequency characteristic for

the

amplification

of

the

controi

signal, approximately 0.5 volt being required

for

full utilization

of

the

compressor. (See Fig.3.21.

5.

Set

COMPRESSOR VOLTAGE and OUTPUT LEVEL

to

maximum (fully

clockwise).

36

17

6. Feed

the

voltage

to

be measured

to

the

recording

instrument,

e.g.

the

Level Recorder

2305.

7.

Set

COMPRESSOR SPEED

to

required value.

8. Regulate

the

desired

output

voltage by

turning

COMPRESSOR VOL-

TAGE

knob

counter-clockwise.

Note: When

the

Beat Frequency Oscillator

is

used

in

conjunction

with

the

Level Recorder

2305

the

writing speed

of

the

Level Recorder should be

kept

below

the

regulation speed

of

the

compressor.

It

is

also possible

to

obtain

different

regulation characteristics

dependent

on

the

position

of

the

potentiometer

marked OUTPUT LEVEL. This can be

seen

from

Fig.3.2.

F. AUTOMATIC RECORDING

By

combining

the

1022

with a Level Recorder

2305

or

using an Auto-

matic

Frequency

Response Recorder

3308,

it

is

possible

to

automatica"y

record

the

frequency

responses

of

four

terminal networks.

The

fo"owing

procedure

should

be

adopted:

1.

Set

up

and

calibrate

the

oscillator as above

in

A.

2.

Connect

the

instruments

as shown

in

Fig.4.2.

The

flexible driving

shaft

(UB

0041)

should be

connected

to

the

upper

driving

shaft

of

the

Recorder, DRIVE

SHAFT

I (Fig.4.3.).

The

other

end

should

be con-

nected

to

the

drive

socket

on

the

left hand side

of

the

1022

(Check

engagement

by

switching on

the

Level Recorder

and

the

magnetic

clutch

of

the

1022

and

note

if

the

scale

pointer

rotates).

3.

Set

PAPER DRIVE

to

"Stop,

Forward".

4. Select

and

insert required Range

Potentiometer.

(NB: Place POTENTIOMETER RANGE

knob

to

"Standby"

when

changing

potentiometers).

5.

Set

POTEf'JT!O

~

~ETER

RANGE knob

to

CO

ri

es

pond

to

the

Range

Potentiometer

being used.

Example:

50

dB Range

Potentiometer

.

Paper Speed

100

mm/sec.: Use

the

section

"50

dB 10

mm/sec."

and divide

the

measured result by 10,

BRUEL & KJAER 1022 User guide

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