fect. In the attenuation range of the low pass filter the modulation is further re -
stricted.
3.4. Vibration Displacement
The vibration quantity most easily observed is displacement, also known as the de-
flection of the vibration. It is formed by double integration of the acceleration. In
comparison to velocity, the practically usable frequency range is even more re-
stricted. On the one hand it requires a high pass filter in order to attenuate low frequency
noise signals, which would otherwise appear amplified in the measurement values be-
cause of the double integration. On the other hand, frequencies in the range of less than
one hundred Hertz are so strongly dampened that an evaluable display value is no longer
recognizable.
Due to these restrictions, displacement measurements should only be applied where ac-
celeration or velocity is not capable of delivering the desired assessment.
The VM24 measures the vibration displacement from 5 to 200 Hz. The frequency re-
sponse diagram is shown in 6. The curve ends at 200 Hz because even in the case of a
fully modulated sensor only single digit measurement values still occur.
The following formula applies to sinusoidal signals which have been formed through
double integration:
d
=
a
(
2
Π
f
)
2
7
Figure 6: Frequency response curves for displacement
1
10
100
1000
0,001
0,010
0,100
1,000
10,000
d: 5Hz-200Hz
Hz
m
m
