B&K 2250 Light Manual do Utilizador descarregar pdf (Página 53)

CHAPTER 5

Calibration

The automatic calibration reminder facility will pop-up a reminder approximately 2 months

before your next calibration is due and keep on reminding you every week until you do one of

the following actions:

• Send your instrument for Accredited/Traceable Calibration and update the Last

Calibration date

• Check the ‘Do not ask/remind again’ checkbox in the reminder pop-up (see example in

Fig.5.7)

• Disable the automatic calibration reminder

Fig.5.7

Reminder pop-up

You can set the Calibration Interval parameter to either 12 months or 24 months depending on

your local requirements.

You can disable the facility by selecting the Automatic Calibration Reminder parameter to Off.

5.7 Charge Injection Calibration

5.7.1 Theory of Charge Injection Calibration

If an external sound source is not available, for example during short or long term monitoring,

you can check the calibration of the analyzer using the Charge Injection Calibration (CIC)

facility. This is done automatically during a logging measurement (see section 11.2). Unlike an

internal calibration, the Brüel & Kjær patented CIC technique enables a complete

measurement chain to be verified, including the microphone, the preamplifier, the cabling and

the analyzer. Each verification measurement is compared to an initial reference measurement.

As the name implies, the method uses injection of charge into the microphone and preamplifier

input circuit, and the ratio between the measured signal and the injected signal is measured

(CIC Ratio), see Fig.5.8.

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B&K 2250 Light Manual do Utilizador Página 53