BRUEL & KJAER 1022 - Mechanical Measurement Applications

BRUEL & KJAER 1022

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GROUP

C.

MECHANICAL

MEASUREMENTS

Strain

Measuremen~s

on

Vibrated

Objects.

In

the

measuring

of

mechanical

strain

on

objec

ts

under

vibration,

it

is

essential

that

the

vibration

acceleration

is

kept

constant

within

the

range

of

frequencies

at

which

measurements

are

being

taken

and

that

inherent

resonances

in

th

e

sys

t

em

have

no

effect

on

the

magnitude

of

the

driving

force.

JJ

2103

~

..

•.

• ••

•.

~

-.

;;

..

~

.

--

.

=:.

:

.

!

Fig. 3.18a.

Arrangement

for

measurement

of

vibration in

small

mechanical

constructions.

The

illustration

in

Fig.

3.18a

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.

To

keep

the

acceleration

cons

tant

a

controlling

system

is

utilized.

This

system

consists

of

an

Accelerometer

Type

4308

mounted

on

top

of

the

te

,

st

object

. As

the

acceleration

has

to

be

cons

t

ant

and

under

contro

l

the

output

voltage

is

connected

via

a

Cathode

Follower

Adaptor

J J 2612,

Cathode

Follower

2613,

and

a

Microphone

Amplifier

2603 to

the

compressor

input

of

the

B.F.O.

The

filter

switch

on

the

Type

2603

shou

ld

be

set

to

position

"Linear".

40