Bruel & kjaer 1405 User manual

Noise Generator

Type 1405

A highly stable random noise generator

pro-

ducing

white noise up to 100 kHz, white noise

up to 220 kHz (both with a standard spectral

density

of

10

-4

V2

/Hz) and

pink

noise

up

to

50

kHz. All three random signals can be

stopped

without

extraneous noise

either

manually

or

remotely.

The instrument contains a - 3

dB

/Octave

filter

and a Compressor

circuit

both of

which

can be

used independently.

BRilEL&

K\.IAER

Power

Compr. Voltage

Compr. l

np

ut

~

.Compr.~

dS/,

1405

Noiie Generator

Type 1405

Compression

"

WI'>,leNo.

..

Pinl<No.u

20

kJot.t

. 50

~HI

Gen. StOP

Output

@

RANDOM

NOISE

GENERATOR

TYPE

1405

January

1974

CONTENTS

1.

INTRODUCTION

AND

SPECIFICATIONS

(PRODUCT

DATA)

........

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

........

..

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

..... 1

2.

CONTROLS...

..

.........

.......

.....

.......

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

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

...........

..

........

...........

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

......

3

2.1 . FRONT PANEL ........

..

....

..

....

..

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

....

..

....

.........

..

....... 3

2.2

.

REAR

PANEL

..

.....

..

..........

..

....

..

....

.. ..

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

..

.

..

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

..

........

.........

..

4

3.

OPERATION

AND

APPLICATIONS

...........

.........

..

.........

.

..

...........

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

..

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

... 6

3.1. PRELIMINARY ADJUSTMENTS

..

.........

..

.......

.

.......

..

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

6

3.2

.

BATIERYPOWER

..

......

........

..

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

.. ..

...

........

...

.........

.

.. .. ..

..

........ 7

3.3. OPERATION AND APPLICATIONS

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

...

.. ..

.

..

.....

..

.....

..

..........

..

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

7

Mode1;

Wh

ite Noise,

100

kHz

~.....

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

..

.

..

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

.

..

......

....

..

.....

7

Mode

2;

White

Noise,

20

kHz

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

...

..

.....

...

.. ..

...

..

......

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

8

Mode

3; Pink Noise,

50

kHz

..

...

......

..

...

.. ..

.......

........

..

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

.....

..

... 9

Mode

4; Pink Noise,

-10

dB

..........

..

......

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

..

......

..

........

.....

12

Mode

5;

Filter,

-3

dB/Octave ....

..

.

.. ..

..

.. .. ..

...

..

......

..

...

.. ..

...

..

......

..

.

.......

..

....

13

Calibration

pf

Power

Spectral

Density

Levels

.. ..

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

..

.......

..........

.......

..

13

Mode

; Compressor

Only

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

..

....

..

....

.....

..

.

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

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

..

.......

15

Setting

up

of

the

Compressor Loop

..

...

..........

.

..

....

..

......

..

.

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

........

15

4.

DESCRIPTION

.....

..

.........

.....

..

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

...

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

........

.

..

.....

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

.......

..

17

4.1. RANDOM NOISE OUTPUTS .....

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

.

..

.

.. ..

.....

..

....

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

17

4.2.

THE

-3

dB/OCTAVE

FILTER

..

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

..

.....

.......

..

........

.. ..

......

..

........

.. ..

.

19

4.3.

THE

COMPRESSOR CIRCUIT ............

..

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

..

.

..

.

.......

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

20

FEATURES:

•

White

Noise

in

the

frequency

range

20

Hz

to

100

kHz

•

Uniform

spectral

density

10-

4

V2

/Hz

•

Pink

Noise

in

the

frequency

range

20

Hz

to

50

kHz

•

Built

-

in

-3

dB/octave

filter

can be used

separately

• Bui

lt

-

in

compressor

amplifier

with

meter

•

Six

compressor

speeds

•

Signal

/

hum

ratio

better

than

90

dB

•

Manual

and

remote

generator

stop

•

Mains

or

ext.

battery

operation

USES:

•

Sound

insulation

measurement

•

Frequency

response

measurement

•

Vibration

testing

• Electro

acoustic

measurements

• Reverberation

measurement

•

Sound

distribution

measurement

• Cross

talk

measurement

•

Signal

to

noise

ratio

measurement

on

commun

i

cation

lines

13

- 1

09

type

1405

Noise

Generator

Noise Generator

Tvpe 1405

Power

Gen.

Stop

Campr. Voltage Compression

dB

Output

Compr. I

nput

10 .

3 ·

Compr

. Speed

dB

ls

100

JOO

.. Whlt, No,,. P

,nk

Noist

20

kHz

50 kHI

..

Comp-,

Only

Output

@

Brliel&

Kj<ef"

The Noise

Generator

Type 1

405

is

designed

to

supply

well

defined

white

noise

in

the

frequency

range

20

Hz

to

100

kHz.

The

generator

has

a

built

-

in

- 3 dB/octave

filter

which

is used

to

weight

the

white

noise

in

order

to

produce

pink

noise

in

the

frequency

range

20

Hz

to

50

kHz.

The

filter

may

also be used sepa-

ra

tely

for

other

weighting

purposes

such

as

automatic

bandwidth

com-

pensation

.

The

generator

also con-

tains

a

compressor

amplifier

which

is

useful

wh

en

performing

frequency

response

measurements

in

various

applications

within

the

fields

of

sound

and

vibration.

In

such

cases

the

noise

generator

is

often

com-

bined

with

a

filter

in

order

to

obtain

a

narrow

band

signal

which

is

then

used

to

control

the

compressor

.

Also

the

compressor

amplifier

may

be

used

separately

.

The

Type

1405

is

built

-

into

a

standard

B & K cassette

which

en

-

ables easy

combination

with

other

instruments

and

mounting

in

racks

(for

example

with

Power

Amplifier

Type

2706

for

high

output

power)

.

Description

The

white

noise

is

made

in

the

generator

(see block

diagram

Fig.1)

which

is

built

up

around

two

zener

diodes kept at

constant

temperature

in

an oven. It has a

uniform

spectral

density

of

10

-4 V2/ Hz.

The

signal

from

the

generator

is passed

on

to

the

first

of

two

filters

via an

attenuator

which

sets

the

output

level.

The

signal

from

the

attenuator

can

be

short

-

circuited

to

stop

the

output

, a

feature

necessary

for

reverberation

measurements

.

The

generator

stop

can

be

controlled

manually

as

well

as

automatically

.

The

two

low

pass fi

lter

/

amplifier

sections

limit

the

upper

frequency

of

the

white

noise

signal,

the

first

to

100

kHz and

the

second

to

20

kHz.

Both

filters

are

3 pole

filters,

the

second is

of

the

Chebichev

type.

The

output

signals

from

the

filters

are

available, via

the

mode

switch,

at

the

output

of

the

generator

.

The

20

Hz

to

100

kHz

signal

from

the

output

of

the

first

filter

is

also

I

fed

to

a

-3

dB/octave

weighting

network

in

order

to

make

a

pink

noise

signal

in

the

frequency

range

20

Hz

to

50

kHz.

The

mentioned

output

signals

are

also

fed

to

a

compressor

amplifier

system

which

compresses

them

according

to

the

signal

present

at

the

compressor

input

.

The

degree

of

compression

can be

read-off

the

built-in

meter.

Mode

Switch

2 1 Gen.Output

Output

LP

Generator

---

Voltage

r---<r--

Filter

Amplifier

r---<

~

Filter Amplifier

~

3 / 0

R

egu

lator

100

kHz

20

kHz 4

~

°6

/ IExt.

Gen.

/

I /

Input)

/

~---------

/

! oV

r--

Ma

nual

Pink Noise

Remote Generator

Filt

er

0

~ontr

ol

Control Stop - 3

dB

/

f------01

°

oc

t

ave

@Compressor

Input

IFilter Input)

Working

Modes:

1.

Output

of

white

nois

e

in

the

fr

equency

range

20

Hz

to

100

kHz

with

uniform

spectral

density

of

10

-4

V2

/Hz (Up to

50

kHz)

2.

Output

of

white

noise

in

the

fre

-

quency

range

20

Hz to

20

kHz. Level

within

± 1 dB in

the

range.

Fall

off

slope above

20

kHz:

>

18

dB/octave

3.

Output

of

pink

no

ise

(white

noise

de-

creasing 3 dB/octave) in

the

fre

-

quency

range

20

Hz to

50

kHz

within

± 1 dB

4.

Same

as

mode

3

but

at

a

10

dB l

ower

level. (Used

when

1405

is

comb

in

ed

with

1/ 3 Octave Filter

Set

1616)

I I

Compres-

sor

Int

eg

r

ator

Volta

ge

r--

Rectifier r-- R

efe

r

ence

Regulator

/

Fig.

1.

Block

diagram

of

Type

1405

Specifications 1

405

5. Use as a - 3 dB/octave

filter

6.

Use as a

compressor

amplifier

.

Amplitude

Distribution:

Symmetrical

Gaussian

with

crest

factor

up

to

five

Output

level

:

Calibrated

output

: 3,

16

V RMS in

100

kHz pos.

Continuously

variable

down

to 0 V

Output

load

Impedance:

Output:

'"

5 kO

Compressor

Output

:

'"

5 kO

Signal

to

Hum

Ratio:

>

90

dB

for

"w

hite

noi

se"

output

>

70

dB

for

"pink

noi

se"

ou.!put

Stability

of

Output

level:

Be

tt

er

than

±

0,3

dB in

the

range -

10

°

to

40

°C

Compressor

:

Speed: 3 -

10

-

30

-

100

-

300

-

1000

dB/ s

Range: >

80

dB

Min

.

input

signal: 0,5 V avg

Max

.

input

signal: 9,5 V avg

r----

I--

Compre

ssor

Amplifier

r-

AGC

-::-@

Amplifier Output

I +

Compres- Compres-

sor

Speed

Meter

/

473012

Input

imp

e

danc

e:

>

18

kO on

compressor

input

82

kO

on

ext. gen.

input

Frequency range:

20

Hz

to

200

kHz

Meter

:

Calibrated

in dB

compression

(min

.

compr.

at 0 dB)

Distortion

: approx. 1%

with

3 V RMS on

ext.

sine

gen.

Generator

Stop

Function

:

Operated

manually

or

re

motely

.

Remote

operation

: 5 V positive logic,

contact

or

a

DC

voltage

o

to

2,5 V:

Stop

,

2,5

to

20V

:

signal

Power

Supply

:

110

,

115

,

127

,

150

,220,

240V

AC

±

10

%

50

-

60

Hz

, approx. 5 W

Batteries

: 2 x

22

to

30V,

2 x 2 W

Dimensions

(KK

0025

cassette):

He

ight

:

132

,6

mm

(5,2

in)

Width

:

209

,5

mm

(8,3

in)

D

epth

:

200

,0

mm

(7,9

in)

Weight:

2

kg

(4

,5 Ib)

Accessories

Included

:

Spare

lamps

, fuses,

power

cord

2.1.

FRONT

PANEL

Power

___

.....

__

-I

Compr. Voltage

Compr.

Voltage--+---1

Compr. I

nput

Compr. InpIJt

___

+

__

-H~

POWER:

COMPR. VOLTAGE:

COMPR. INPUT:

COMPR. SPEED:

MODE SWITCH:

10 .

3 ·

2.

CONTROLS

Compf. Speed

dBls

100 300

..

Noise Gene

rato

r

Typ

e 1405

Compression

dB

White Noise

Pmk

HolM

20

kHz

SO

kHz

..

Compr.

Sp

ee(j

----'

Fig.2. 1.

Front

Panel

Gen.

Stop

~

__

-+

____

Gen. Stop

Output

t---t-----output

Control

Mo(je Swi

tc

h

113581

Toggle

switch

for

turning

the

instrument

on.

When

the

instrument

is

turned

on, the

meter

lamp

should

light.

Knob

for

adjustment

of

the

compressor voltage.

Turning

the knob

anti-

clockwise

will

increase

the

compressor voltage, increase the degree

of

compression and decrease

the

output

signal level.

B & K co-axial socket

which

accepts plug JP

0101

for

input

of

the

com-

pressor control signal. This socket is also used

for

input

to

the

-3

dB/Octave

filter.

Knob

for

adjustment

of

the

compressor speed. In

the

position "Compr.

Off"

the compressor voltage

will

be removed

from

the

system.

Allows

selection

of

the

instrument

mode, six being available. These

are:

"

White

Noise 1

00

kHz"

:

the

instrument

outputs

a

white

noise signal

from

20

Hz to 1

00

kHz.

3

OUTPUT:

OUTPUT CONTROL:

GEN. STOP:

COMPRESSION METER:

2.2.

REAR

PANEL

"White

Noise

20

kHz": the

instrument

outputs

a

white

noise signal

from

20

Hz

to

20

kHz.

"Pink Noise

50

kHz":

the

instrument

outputs

a

pink

noise signal (fail-

ing

at

3 dB/Octave)

from

20

Hz

to

50

kHz.

"Pink

Noise

-10

dB":

the

instrument

outputs

the

pink

noise signal

as

above

but

decreased in level by

10

dB.

"Filter

-3

dB/

Oct

." :

allows

the

instrument

to be used

purely

as a

-3

dB

/Octave

filter.

"Compr.

Only"

:

allows

the

instrument

to act

purely

as a compressor

amplifier

.

B & K co-axial socket

which

accepts plug

JP

0101

for

output

of

the

compressed signal.

For

adjustment

of

the

random noise

output

level. In

the

position

"Cal.",

fully

clockwise,

if

the

instrument

is in

either

of

the

two

white

noise modes,

the

instrument

will

output

a signal

of

spectral

density

10-

4

V2

/Hz.

Push-button

operated noiseless

switch

for

turning

the

instrument's

Random Noise

Generator

off.

Indicates

the

degree

of

Compression

between

0 and

aOdB.

2:

Wh

ite No

ise

20 kHz

3: Pink Noise 50 kHz

4: Pmk

No

ise

·-

10

dB

5: Filter - 3

dB

/Oct.

6: Compr. Only

Gen. Remote Control

Output

Ou

tput

Made in Denmark

ComDress,or I

nput

Output

Gen. Remote 1

73622

POWER SOCKET:

MAINS

VOLTAGE SELECTION:

4

Fig. 2.2. Rear

Panel

For connection

of

the AC

mains

supply. For

connections

see

Fig.2.3

.

To select

the

correct AC

mains

supply, remove the central fuse holder

and

turn

the

selector

with

a

wide-bladed

screwdriver

or small coin.

Blue N

eu

t

ra

l

AC Power

I"J

B

row

n

Su

pp

ly

Li

v

[

I~

J

Gr

een

a

nd

Ye

llow Grou

nd

172246

Fig.2.3. Connections to the POWER socket (External View)

REMOTE CONTROL: 7

DIN socket

which

accepts plug

JP

0703

for

remote control

of

generator

stop and application

of

external battery

power

. For connec-

tions

see

Fig.2.4

.

GEN

. OUTPUT: BNC socket

for

output

of

random noise signals,

output

from

-3

dB/Octave

filter,

and

input

of

signal

from

an external generator

for

compression, as selected by

the

MODE SWITCH.

OUTPUT: BNC socket

in

parallel

with

B &K socket on

front

panel

for

output

of

the

compressed signal.

COMPRESSOR 'INPUT: BNC socket in parallel

with

B & K socket on

front

panel

for

input

of

compressor control signal.

22-30

V

DC

2

2-3

0V

DC

173600

Fig.

2.4

. Connections to the REMOTE CONTROL socket (External

View)

5

3.

OPERATION

AND

APPLICATIONS

3.1

.

PRELIMINARY

ADJUSTMENTS

6

Before

the

instrument

is connected

to

the

mains

supply

the

voltage selector on

the

rear

panel

should

be checked

for

the

correct

voltage

setting

. If

adjustment

is required,

push

and

turn

the

central

fuseholder,

remove

it

and

adjust

the

voltage selector

to

the

correct

mains

voltage

using

a

small

coin

or

wide-bladed

screwdriver

. Replace

the

fuse and fuse-

holder

.

In any

measurement

system

using

several

instruments

grounding

considerations are

im-

portant

. In general

to

avoid

ground

loop and noise problems, all

the

instrument

signal

grounds

should be connected, and

the

signal

ground

of

only

one

of

the

instruments

should

be connected

to

mains

ground.

The

1405

has an

internal

switch

which

enables

the

connection

between

signal

ground

and chassis

ground

to be removed

if

necessary. The

switch

is

shown

in

Fig.3.1.

Fig. 3. 1.

The

Signal

Grounding

switch

The

switch

can be located by

standing

the

instrument

on

its

left

side as

viewed

from

the

front,

releasing

the

knurled

nut

on

the

front

panel and removing

the

bottom

panel

of

the

instrument.

The

switch

will

then

be visible close

to

the

mains

connection

socket.

As

delivered, and as

shown

in Fig.3.1

the

switch

makes

the

connection

between

signal

ground

and chassis

ground.

This

configuration

can be used in

the

following

circum-

stances:

when

none of

the

instruments

in

the

system

are

connected

to

mains

ground,

when

the

1405

is

the

only

instrument

connected

to

mains

ground

e.g. via a

three

mains

socket.

The connection should be removed in the

following

circumstance

:

when

any

of

the

other

instruments

in

the

system have

their

signal grounds con-

nected to

mains

ground.

3.2.

BATTERY

POWER

To

power

the

1405

with

batteries,

two

22-30

V

DC

batteries are required, the

power

consumption

from

each being approximately 2 W. Connection

of

battery

power

is made

to

the

8

DIN REMOTE CONTROL socket on

the

rear panel. The necessary connec-

tions

are

shown

in Fig.3.2.

22-30V

+ +

22-30

173582

Fig. 3.2. Connections to

the

REMOTE CONTROL socket

for

External

Battery

Power

(External View)

3.3.

OPERATION

AND

APPLICATIONS

As

the

Noise

Generator

Type

1405

is a versatile

instrument.

its operation

will

be de-

scribed

in

six set-ups, each corresponding to one

of

its modes

of

operation. The applica-

tions

given are intended to

show

the

full

capability

of

the

1405.

The

instrument

is ne-

vertheless

suitable

for

applications

that

are less demanding

than

those given in

this

sec-

tion

.

3.3.1.

Mode

1;

White

Noise,

100

kHz

The application given

for

this

mode is

the

determination

of

the

response to random noise

of

an electronic

circuit.

A typical set-up is

shown

in Fig.

3.3

.

The

1405

controls

should

be set

as

follows

:

POWER

COMPR. SPEED

MODE SWITCH

OUTPUT

"On"

"Compr

.

Off"

"White

Noise 1

00

kHz"

"Cal."

The response

of

the

test

circuit

to random noise is

shown

analyzed

in

Fig.

3.3

by a Heter-

odyne Analyzer

which

is a

narrow

constant

bandwidth

analyzer. The

1405

output

in

this

mode is

flat

within

± 1 dB

from

20

Hz

to

75

kHz,

allowing

the

test

circuit

response to be

obtained in

this

frequency

range. In

this

mode

the

1405

has a standard

output

of

10

-4

V2

1Hz,

allowing

the

gain

of

the

test

circuit

to be

immediately

calculated

knowing

the ana-

lysis

bandwidth

and voltage

output.

For instance

if

100

Hz

bandwidth

is used,

then

a vol-

tage

output

of

0,1 V

(v,

0 - 4 .

100)

will

correspond to

unity

gain

through

the

test

cir-

cuit

.

Alternatively

if

the

power

spectral

density

(in

V2

1

Hz)

of

the

analysis is required, the

bandwidth

compensation

facility

of

the

Heterodyne Analyzer and

meter

scale

SA

0055

can be used.

7

BRUEL & KJAER 1405 User manual

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