Group C. Mechanical Measurements - BRUEL & KJAER 1022 Instructions And Applications

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 tem have no effect on the magnitude of the driving
force.
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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 constant a controlling system is utilized. This
system consists of an Accelerometer Type 4308 mounted on top of the te, s t
object. As the acceleration has to be constant and under control 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 should be set to position
"Linear".
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