© PCE Instruments
7
18 Calibration
To make a calibration, use a 94 dB, 1 KHz noise calibrator.
Set the meter as follows:
Frequency weighting: A
Time weighting: FAST
Measurement range
: 50 … 100 dB
Turn on the calibrator and choose the 94 dB option. Now remove the
windbreak from the microphone and place the noise calibrator on the
microphone. Compare the reading that is displayed on the device with
the value set in the calibrator. If there is a deviation between the
values, you can change the displayed value with the adjustment
screw.
Note:
it is recommended to calibrate the meter on an annual basis.
19 Further measurement errors
There are two possible sources of error causing incorrect readings. It
is possible that the human body as well as the case of the meter
absorb and reflect sound waves. The difference can be up to 6 dB at
a distance of 1 m and a frequency of 400 Hz.
The absolute ambient pressure is the second source of error. The
absolute ambient pressure can change depending on the altitude of
the meter. The displayed reading must then be compensated using
the following chart.
Altitude (m)
Pressure (mbar)
Compensation (dB)
0
… 250
1013
… 984
0.0
>250
… 850
983
… 915
-0.1
>850
… 1450
914
… 853
-0.2
>1450
… 2000
852
… 795
-0.3
Alternatively, you can calibrate the meter before each measurement made at a different ambient
pressure.
