Casella-cel CEL-281 Manual do Utilizador descarregar pdf (Página 128)

pressure, the CEL calibrators generates a nominal 1 kHz signal

with a level of 114.0 dB at the microphone. The dosimeter dis-

play should indicate 114.0 dB (A) in the following format:

: dBA

However, with a replacement microphone, the level may well

be several dB different, so that the digital section of the instru-

ment must be re-trimmed before an accurate calibration can be

achieved.

16. Use the and keys to change the display so that the

trimming range of the microphone can be determined.

These keys give +0.05 dB or -0.05 dB increments respectively,

over a total correction range of ±2 dB. However as the display

resolution is 0.1 dB, two key presses are needed to produce an

observable change in the displayed value. In calibration mode

these keys have an automatic repeat function when held down.

For example, these keys may be found to change the display

from 115.3 to 119.3 dB.

17. Use the and keys to set the display in the exact

centre of this range.

117.3 dB in the example.

The digital section has now been trimmed for the replacement

microphone.

Caution

DO NOT touch the prominently positioned

potentiometer located beside the display on

the upper circuit board

Technical Information

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Casella-cel CEL-281 Manual do Utilizador Página 128