Press the F3 key to open the main menu and select “Human vibration” / “Hand-Arm
ISO 5349”/„Health“. After returning to the measurement screen (Figure 10) you can
check the settings by pressing F1.
Measurement can begin when the sensor and the worker's hands have been placed
on the handle of the object carrying out the operation. To start the measurement
press the key ► (Reset). This will result in the following:
•
the RMS values of X/Y/Z, the vector sum a
W
and MTVV reset to zero
•
the measurement timer restarts.
Pressing Reset before a measurement is mandatory to establish defined start condi-
tions.
The RMS values of X/Y/Z and the vector sum are averaged over the entire measur-
ing time. That's why fluctuation becomes less the longer the measurement takes. Af-
ter a while short shock pulses have almost no influence on the displayed results .
Recommended measuring time for hand-arm vibration is at least 30 seconds. The
measuring timer in the upper right corner remains red until 30 second have elapsed.
“OVERLOAD” is indicated instead of the measuring values if the current magni-
tude is too high. Even if the overload condition was of short duration the measured
interval RMS value may become invalid because of missing samples. An overload
event during the entire averaging time is indicated by “OVL!” in the upper right
corner after the date. This warning can be deleted by pressing the key ► (Reset).
After measurement you may save the results by
pressing the key ▼. Measurement should be contin-
ued or finished immediately before pressing the key.
Otherwise the measuring values will drop slowly.
You will be asked to enter two lines of ten capital let-
ters or numbers as a comment (Figure 12). Use the
keys ◄▲▼► to select characters and to change the
input position. Press F1 to change the input line.
Measurement can be finished before entering the
comment because the results have already been saved
when pressing the key ▼.
Measurements can only be saved if a sensor is de-
tected at X/Y/Z and if there is no overload condition.
In these cases the VM31 will display “Sensor error” or “Overload occurred” instead
of saving in order to avoid invalid recordings. If an overload occurred since the last
reset (“OVL!” in upper right corner) the instrument will show a warning “Overload
occurred after last reset! Save anyway?”.
If you want to measure several partial exposures you may do further measurements
(see section 3.2).
For the calculation of
vibration exposure A(8
) and to store results on a PC the Ex-
cel macro file vm31.xlsm is provided.
The fourth channel (A) of the VM31 is not active when hand-arm vibration is mea-
sured.
11
Figure 12: Comment