Brüel & kjær 1019 User guide

Automatic

Vibration

Exciter

Control

Type 1019/39

• i

·"=

i

..:~

® ·•.

J

~

-

::"

~

:

-

·

·il

:·

·.

!.,

The

Autom

a

tic

Vibr

a

tion

Exci

ter

Control

is a

spe-

cially

designed

signal

source

for

the

vibration

te

sting

of

mechanical

and

electro-m

e

chanical

components

in

the

frequency

range

5 c js

to

10

kc

/s.

BHUEL&KJJEH

N~rum,

Denmark

eye

80

05 00

.

~

BRUKJA, Copenhagen . Telex: 5316

88

1019

1

10

39

Automatic Vibration Exciter Control

Type 1019/39

NOVEMBER

1965

Contents

1.

Purpose

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.

Description

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1.

Oscillator

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.

Automatic

Frequency

Scan

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3.

Vibration

Derivation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4.

Compressor

Arrangement

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.5.

Meter

Section

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.6.

Frequency

Calibration

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.7.

Remote

Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.8.

Parallel

Operation

of

Generators

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.

Control

l{nobs,

Terminals

etc.

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

11

4.

Operation

as

Vibration

Meter

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

21

4.1.

Setting

to

Mains

Voltage

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

21

4.2.

With

a

Velocity

Pick-up

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

21

4.3.

With

an

Accelerometer

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.

Operation

as

Shaker

Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.1.

Calibration

of

Frequency

Scale

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

24

5.2.

Adjustment

of

Automatic

Frequency

Scanning

Range

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

24

5.3.

Uni-directional

Frequency

Scanning

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

25

5.4.

Partial

Blocking

of

Frequency

Scale

Range

. . . . . . . . . . . . . . . . . . . . 26

5.5.

Setting

of

Scanning

Speed

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.6.

Setting

Regulation

Speed

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.

7.

Possibilities

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5.8.

Setting

Auto

Cross-Over

Frequency

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

30

5.9

Summary

of

Preparatory

Operations

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

30

5.10.

Operation

Schemes

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

31

6.

Operation

with

Level

Recorder

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3b

6.1.

Possibilities

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

35

6.2.

Synchronization

with

Level

Recorder

. . . . . . . . . . . . . . . . . . . . . . . . . . 35

6.3.

Monitoring

Shaker

Table

Motion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.4.

Plotting

System

Frequency

Response

. . . . . . . . . . . . . . . . . . . . . . . . . . 39

6.5.

Recording

Specimen

Vibration

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

41

6.6.

Recording

Two

Quantities

Simultaneously

. . . . . . . . . . . . . . . . . . . . . . 42

7.

Remote

Control

Facilities

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

44

7.1.

Start

and

Stop

of

Frequency

Scan

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

44

7.2.

Forward

and

Reverse

Frequency

Scan

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

44

7.3.

Stand

by

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

44

7.4.

Changing

Scanning

Speed

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

8.

Master-Slave

System

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.1.

Principle

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

46

8.2.

Interconnections

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

47

8.3.

Setting

Up

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

48

8.4.

Adjusting

Individual

Vibrations

(Level

and

Phase)

. . . . . . . . . . . . . . 49

8.5.

Command

of

the

System

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Specification

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

1. PURPOSE

1.

Purpose

The

importance

of

laboratory

tests

which

can

simulate

the

rigorous

vibra-

tions

to

which

components

and

structures

may

be

subject

during

service

has

now

been

fully

recognised.

Depending

on

environmental

conditions

it

is

usual

to

choose

one

(or

more)

of

the

following

three

types

of

excitation

for

these

tests;

viz.

Shock

Random

motion

Sinusoidal

motion

Whilst

it

is

true

that

the

first

two

are

of

great

value

in

the

fields

of

aero-

nautics

and

space

·

technology,

there

is

no

doubt

that

the

sine

test,

and

preferably

a

sine

test

which

sweeps

throughout

the

frequency

range

of

interest,

is

of

most

universal

application.

The

design

engineer

has

come

to

regard

it

as

a

day-to-day

tool

for

determining

the

natural

frequencies

and

Q

values

of

resonances,

and

the

life-test

engineer

uses

such

tests

as

the

basis

of

his

work.

Briiel

& Kjrer

have

been

manufacturing

sweep

sine

generators

for

several

years.

Type

1018

has

been

accepted

the

world

over;

Type

1019

which

re-

places

it

uses

exactly

the

same

fundamental

principles

but

embodies

certain

refinements.

The

Automatic

Vibration

Exciter

Control

feeds

a

shaker

table,

usually

via

a

power

amplifier,

and

the

frequency

of

excitation

is

altered

by

means

of

a

built-in

drive

.

However,

owing

to

the

uneven

frequency

response

of

the

mechanical

system,

the

power

required

to

vibrate

the

test

object

at

a given

Automatic

Vibration

Exciter

Control

r-------.

Velocity

Pick-up

_

_.

___________

__

Shaker

Table 263300

Fig. 1.1. Principle

of

a closed loop vibration test system.

The

accelerometer and

velocity

pick-up

are alternative transducers,

only

the former requiring a pre-

amplifier.

3

1. PURPOSE

level is

dependent

on

frequency.

To

keep

the

vibration

level

constant

what-

ever

the

frequency,

a

signal

measuring

the

motion

of

the

shaker

table

is

fed

back

to

the

Automatic

Vibration

Exciter

Control.

This

completes

a

servo

loop

which

regulates

the

power

output

of

the

exciter

so

that

various

pre

-

determined

test

programmes

can

be

carried

out

under

controlled

conditions.

Either

an

accelerometer

or

a

velocity

pick-up

may

be

used

as

transducer

and

the

vibration

derivation

section

of

the

1019

contains

all

the

integrator

and

differentiator

networks

necessary

for

deriving

acceleration,

velocity,

or

dis-

placement

from

either

input.

It

is

possible

to

hold

any

of

these

dynamic

properties

constant

on

the

shaker

table,

and

also

there

are

two

"auto"

arrangements

in

which

the

quantity

measured

and

controlled

can

be

changed

at

a

predetermined

"cross-over"

frequency,

i.e.

displacement

below

cross-over

to

acceleration

above,

or

velocity

below

cross-over

to

acceleration

above.

All

the

vibration

derivatives

can

be

read

directly

on

the

semi

-

logarithmic

meter

scale

provided

the

velocity

or

acceleration

signals

to

the

inputs

are

scaled

to

96.3 mV

per

inch/sec

or

10

mV

per

g

respectively.

Acceleration

generators

should

be

used

in

conjunction

with

the

Accelerometer

Preampli·

fier

Type

2620.

This

preamplifier

has

graduated

sensitivity

controls,

by

means

of

which

the

sensitivity

of

the

preamplifier

is

set

in

relation

to

the

known

sensitivity

of

the

accelerometer

so

as

to

obtain

e·

xactly

10

mV/g

for

the 1019's

input

.

Signal Generator

••

0 .,. ,..,

·i r

':

i

:·

,.,

·•

··

·-;

::-

i ::

..

, .=• = ·:· ·

1119

Control S

Monitor

Ou

Measuring

Amplifier

t A)

e

Accelerometer

Preamplifier

Graphic

Level Recorder

Fig. 1.2.

Fundamentals

of

a vibration

test

set-up

utilizing

the

Automatic

Vibration

Exciter

Control

Type

1019.

1. PURPOSE

It

is

often

of

interest

to

obtain

a

graphical

plot

of

the

response

of

vibrated

specimens.

This

is

conveniently

achieved

by

synchronizing

the

frequency

scan

of

the

1019

with

the

frequency

graduations

on

chart

paper

running

through

a

Briiel

& Kjrer

Level

Recorder

Type

2305.

One

Automatic

Vibration

Exciter

Control

can

be

set

up

as

a

"master"

to

control

up

to

three

similar

"slave"

units.

In

such

an

arrangement

the

"master"

controls

its

own

shaker

table

as

well

as

the

frequency

of

the

output

signal

from

the

"slaves".

Each

"slave",

however,

can

control

the

vibration

level

of

its

associated

shaker.

It

is

thus

possible

to

synchronize

the

movement

of

up

to

4

vibration

exciters

for

the

testing

of

large

specimens.

Furthermore,

the

phase

relationship

between

the

"master"

and

"slave"

output

signal

can

be

adjusted

over

a

full

360°

angle.

The

Automatic

Vibration

Exciter

Control

Type

1019

(cabinet

version)

can

also

be

supplied

for

standard

19''

rack

mounting

as

Type

1039.

2.

DESCRIPTION

2.

Description

The

principle

of

operation

is

illustrated

in

the

block

diagram

Fig.

2.1

Fixed

Oscillator

Vari-fl

Amplifier

"Compressor"

Socket

Function

Selector

Vibration

Generator

Accel.

Range

Displ.-Vel.

Range

Derivation

A

v

D

Output

Amplifier

"O

scillator

"

Jack

"Vibration"

Jack

~:-.:::~:"

Gen.

Mains

263299

Fig. 2.1. Principle

of

the

Automatic

Vibration

Exciter

Control.

2.1. Oscillator.

6

The

oscillator

works

on

the

heterodyne

principle;

by

beating

together

two

comparatively

high

frequencies-one

from

a

variable

and

one

from

a

fixed

oscillator-an

output

frequency

of

between

5

and

10ooo

c/s

is

produced.

The

fixed

oscillator

oscillates

at

either

30

kc/s

or

35

kc/s,

depending

on

the

setting

of

FREQUENCY

RANGE.

The

variable

oscil-

lator

frequency

is

between

25

kc/s

and

30

kc/s,

as

determined

by

the

position

of

the

main

tuning

capacitor.

There

are

therefore

two

fre-

quency

ranges,

viz.

5-5ooo

c/s

or

5005-lOooo

c/s

The

first,

which

is

covered

in

a

true

logarithmic

sweep,

is

marked

directly

on

the

large

circular

scale.

The

second

range

is

not

logarithmic,

the

frequency

being

reckoned

by

adding

5ooo

c/s

to

the

scale

reading.

2. DE')CRIPTION

2.2. Automatic Frequency Sean.

The

frequency

range

can

be

continuously

scanned

with

various

speeds

by

a

built-in

synchronous

motor

which

can

be

reversed

electrically.

The

motor

speed

can

be

changed

in

six

coarse

steps,

covering

the

range

o.3

to 100

degrees/min.

Within

e·

ach

of

the

six

steps

the

speed

can

be

fine

adjusted

in

22

steps.

Using

bo.th

controls

provided,

there

are

132

possible

scanning

speeds

from

o.3

to

300

degreesfmin.

*)

The

frequency

range

for

to-and-fro

scanning

is

easily

adjusted.

Uni-

directional

scanning

throughout

360° is

also

possible,

the

output

being

cut

dead

while

the

pointer

is

on

the

blank

part

of

the

dial,

and,

if

the

scanning

range

is

to

be

reduced,

while

on

the

unwanted

sectors

of

the

scale.

2.3. Vibration Derivation.

The

input

signal,

which

can

be

from

'

either

an

accelerometer

or

a

velocity

pick-up,

is

processed

according

to

the

following

table,

depend-

ing

on

which

quantity

has

been

selected

by

FUNCTION

SELECTOR.

Table

I.

Frequency-weighting

in

the

vibration derivation section.

Input

\To

read

Acceleration

Velocity

Displacement

Acceleration

Direct

-6dB/Oct.

-12

dB/Oct.

Velocity

+6

dB/Oct.

Direct

-6

dB/Oct.

Note:

Differentiation;

Equivalent

to

slope

+6

dB/Oct.

Integration;

Equivalent

to

slop.:! - 6

dB/Oct.

Considerable

low-frequency

noise

is

inherent

in

any

measuring

system

involving

integration,

so

special

networks

(which

do

not

affect

the

measurements)

are

included

to

reduce

this

and

to

prevent

the

whole

system

from

"hunting".*

*)

In

the

two

"Auto"

positions

of

FUNCTION

SELECTOR

the

relays

governing

which

weighting

function

is

effective

at

a

given

instant

are

switched

at

a

predetermined

generator

frequency,

adjustable

between

8

and

1ooo

c/s.

The

acceptable

ranges

for

measurement

and

control

are

given

on

p.

8.

*

)Additionally

there

are

six

other

scanning

speeds

suit

a

ble for

achieving

synchronism

with

the

frequency-calibrated-paper

transport

on

the

Brfiel & Kjrer Level

Recorder

Type

2305.

**)

This

is a

low

frequency

system

oscillation

which

might

otherwise

occur

when

the

generator

frequency

is a few

thousand

cps.

7

2.

DESCRIPTION

Table II.

Frequency Ranges for Measurement

and

Control.

Displacement

10

20

50

100 200 500 1

000

2000

5000

10000

cfs

Velocity

10

20

50

100

.200

500

1000 2000 5000

10000

cfs

Acceleration

10

20

50

100

200

500

1000

2

00

0 5

000

10000

c/

s

IAuto

D-A

& Auto

V-A

Cross-over I f

:·:

·

!·:·:·

:·

:·:·:

·:

l

:·:

·

:·:·:

-=·:·:

·

:·:·:·

!·:·

:·

:·:·

:·:·:·:

l

:·:·:·

:·:

·:·

:l

:-:-:-:

·:·

:·:·:·:·:

+

:·:·:·:·:·:-=·:·

l

10 20 50

100

200

500

1000

2000 5000

10000

cfs

26g278

Legend:

~

With Veloci

ty

Pic·

k-up

~

With

Accelerometer

C::::::::::j

Limits

for

Cross-over

lt

Exceeding . 5

kc/s

requires

the

H.

F.

range

2.4.

Compressor

Arrangement.

8

Except

when

the

COMPRESSOR

SPEED

switch

is

"Off",

*)

the

vibration

signal

is

fed

to

the

regulation

("compressor"

)

circuits.

Here

it

is

rectified

and

the

resulting

DC is

used

to

bias

a

variable-,u

stage

in

the

g

enerator.

Thus,

if

the

shaker

table

vibration

becomes

too

great,

a

larger

bias

signal

appears

and

the

oscillator

output

drops

until

the

status

quo

is

regained.

The

integration

time

constant

in

the

circuit

which

filters

the

rectified

control

signal

is

very

important

since

it

determines

th

e

*)

The

open-loop

output

voltage from

the

generator

rises

10

dB

as

soon as COMPRESSOR

SPEED is moved

aw

ay from "Off".

Brüel & Kjær 1019 User guide

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