Brüel & Kjær 2240 Guide De L'utilisateur page 26

20 Integrating-averaging Sound Level Meter Type 2240 – User Guide
Note: Type 4231 can also provide a 114 dB signal (see Type 4231 User Manual BB 0910).
Normally, this signal should not be used; however, if a calibration must be performed in a
very noisy environment, you can use this level for calibration. In such a case you must
select the 60 – 140 dB range and adjust the reading to 113.9 dB.
7) Remove the calibrator. It switches off automatically after a few seconds.
Electrical Calibration
An electrical calibration calibrates your sound level meter's electronics only (not the micro-
phone and preamplifier) and is based on a built-in reference signal.
The procedure is as follows:
1) Switch on the sound level meter.
2) Press for 3 seconds until you see the following display:
Fig.4.3
Electrical calibration
display within the 30 –
110 dB range
If Type 2240 is set in the 60 – 140 dB sound level range, the display will instead be like
this:
Fig.4.4
Electrical calibration
display within the 60 –
140 dB range
Note: In both cases, the calibration level is 6 dB below the top of the measurement range,
i.e., 104 dB and 134 dB, respectively, as indicated on the display.
3) Now use the supplied screwdriver to adjust the reading to the required value (104.0 dB or
134.0 dB).
4) Press once to leave the electrical calibration mode.