Whole-Body Health Evaluation
Posture
Position
Direction
Frequency
weighting
Weighting
factor (k)
sitting
seat surface
X / Y
Z
W
d
W
k
1.4
1
Whole-Body Comfort Evaluation
sitting
seat surface
X / Y
Z
W
d
W
k
1
1
feet platform
X / Y
Z
W
k
0.25
0.4
backrest
X*
Y
Z*
W
c
W
d
W
d
0.8
0.5
0.4
standing
feet platform
X / Y
Z
W
d
W
k
1
1
recumbent
under pelvis
X (vertical)
Y / Z (horizontal)
W
k
W
d
1
1
under head
X (vertical)
W
j
1
In railway vehicles:
standing
sitting
recumbent
feet platform
seat/backrest/feet
support. surface, pelvis/head
X / Y / Z
W
b
1
In buildings:
undefined
in buildings
X / Y / Z
W
m
1
Table 2: Weighting filters and factors for whole-body vibration
* Please note that the Z axis points along the backbone for all measurements. For measure -
ments at the backrest with a seat pad accelerometer the sensor will always be in a vertical po-
sition with Z perpendicularly to the backbone. However, to compensate this the VM31 auto-
matically swaps the X and Z axis for backrest measurement.
4.4.2. VM31 Settings
4.4.2.1. Whole-Body Measurement with RMS Values
For the evaluation of hand-arm vibration it is recom-
mended to measure both the interval RMS values of
X/Y/Z and their vector sum a
W
. The VM31 measures
these four values simultaneously. In addition it
shows the maximum running RMS (Maximum Tran-
sient Vibration Value, MTVV) which may indicate
the presence of shock vibration. MTVV is not al-
ways the maximum value of the three single RMS
values of X/Y/Z since these are multiplied with
weighting factors (see table 2) which is not the case
for MTVV.
The following section explains the measurement of
whole-body vibration in terms of health risks. Health
evaluation is done with weighting filter Wd for X/Y
and Wk for Z and with weighting factors 1.4 for X/Y
13
Figure 14:
Whole-body measurement