9.2.1.10. Combined Weighting Filters
The weighting filters described in the preceding sections can be applied for measurements in all
three directions (X / Y / Z). Additionally, the following useful combinations are available:
W
d
+ W
k
:
This combination of the filter W
d
for the X and Y axes with W
k
for the Z axis is used
for measurement of whole-body vibrations in seated position at the seat surface.
W
d
+ W
c
:
This combination of the filter W
d
for the X and Y axes with W
c
for the Z axis is used
for measurement of whole-body vibrations in seated position at the backrest.
Important notice:
The measuring axes (X/Y/Z) of the VM30-H refer to the marking on
the seat pad accelerometer. For measurements at the backrest or under the back of a
recumbent person, the axis definition differs from ISO 2631. According to the standard
the Z axis shall always point into the direction of the spinal column. However, the Z axis
measured by the VM30-H will point vertically to the back in the mentioned cases. To
compensate this, the displayed X and Z values must be swapped.
9.2.2. Band-Pass Filters
Band-pass filters differ from weighting filters by their linear passband response. They are used
for various applications, such as machine monitoring and building vibrations.
The VM30-H contains the following band-pass filters:
•
0.4 - 100 Hz
for the measurement of building vibrations to DIN 4150
•
2 - 300 Hz
for measurements at slow running machinery to ISO 10816-6
•
0.4 -1250 Hz
•
10 -1250 Hz
for machine vibrations (vibration severity) to ISO 10816-1
•
0.4 Hz - 10 kHz
maximum bandwidth of the VM30-H
•
1 kHz - 10 kHz
for bearing vibrations
These band-pass filters are only available if acceleration has been selected as vibration quantity.
For vibration velocity only the filters 2 - 300 Hz and 10 - 1250 Hz can be selected due to the
limited frequency response after integration. Vibration displacement can only be measured
between 6 and 200 Hz.
The following diagram shows the frequency response curves of all band-pass filters.
Figure 20: Frequency response curves of the band-pass filters
23
0,001
0,01
0,1
1
10
0,1
1
10
100
1000
10000
100000
Hz
0,4-100Hz
0,4-1250Hz
2-300Hz
10-1250Hz
0,4-10000Hz
1000-10000Hz