MMF VM30-H, Instruction Manual, Page: 31 / 58

9.3.5. Vibration Total Value (A
hv
)
Vibration Total Value with the display abbreviation “Ahv” is determined from vibration in three
orthogonal directions, is calculated as follows
2 2 2 2 2 2
hwz z hwy y hwx x hv
a k a k a k A
+ + =
where
a
hwx
, a
hwy
, a
hwz
are the interval RMS values of X / Y / Z axes
k
x
, k
y
, k
z
are multiplying factors
After the selection of the Vibration Total Value you will be asked for the multiplying factors k
x
,
k
y
and k
z
. These factors can be used for individual weighting of the three axes. Values between 0
and 2.0 can be entered. This may be useful when the triaxial Vibration Total Value is measured
in one or two directions only. Deactivated channels are considered as zero. The dominating axis
with the highest magnitude can then be multiplied by a correction factor between 1.0 and 1.7
(see ISO 5349-1).
The factors k
x
, k
y
and k
z
are also used for the measurement of whole-body vibration to
ISO 2631-1.
When measuring the Vibration Total Value, the VM30-H automatically sets the measuring
ranges of all three channels to the highest one of the three selected ranges.
If autoranging has been activated, a message is displayed after the selection of Ahv, showing
that autoranging is not available in this mode and the gain of all channels is set to 0.1,
corresponding to the highest measuring range. Another range can be selected manually, if
desired (see section 10).
If an overload occurs during the measurement of Vibration Total Value, a message
OVER
LOAD is displayed instead of the measuring value until normal magnitudes are measured again.
Additionally a message Overload is displayed in the center above the measuring value,
alternating with the filter type (Figure 10). It indicates that an overload occurred in at least one
channel during the entire integration time. It can be reset by starting a new measurement using
the ESC key.
The Vibration Total Value is mainly used for human vibration measurement. However, with the
VM30-H it can also be applied for measuring velocity and displacement.
9.3.6. Peak Value (PEAK)
Peak value with the display abbreviation “PEAK” is the highest absolute magnitude (negative or
positive) of the instantaneous vibration signal (human vibration, acceleration, velocity or
displacement) over a measuring period of one second.
If an overload occurs during the measurement of the peak value, a message
OVER LOAD is
displayed instead of the corresponding measuring value until normal magnitudes are measured
again.
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