Rated Force And Limits - BRUEL & KJAER System V Instruction Manual

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F/g . 7.2 . Frequency response of a General Purpose Head 4812
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Frequency response of a B/g Table Head 4813
Shown in Fig.7.3 is the frequency response of the Type 4813 Head. Here there is no sig­
nificant de-coupling step and the acceleration remains level from 150 Hz to 3 kHz. The
resonance is at 5,4 kHz.
It can be readily seen in all three cases that the Exciter can be operated in the region
where the acceleration curve is flat without the use of a compressor loop to controi the
oscillator.
7,1.2 . Rated Force and Limits
When it is desired to vibrate a test object of mass m with an acceleration a, the required
force is:
F
=
(m
+
me) a
where me is the mass of the moving element. In this way, the maximum shaker playload
for a given acceleration level can be computed.
For example :
- mel
~
-
- ­
44