B&K 2250 Light, Руководство пользователя

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46
2250 Light – User Manual
A stable CIC Ratio means a ‘healthy’ system and assures stable operation of microphone,
cable, preamplifier and the remaining measurement system.
Fig.5.8
Charge Injection Calibration. Low-leakage resistance capacitor C
c
is set in parallel with
the microphone and fed with voltage e
i
. The ratio e
o
/e
i
is constant when g, C
c
, C
m
and
C
i
are constant. Changes to preamplifier gain (g), cable parameters, microphone
capacitance (C
m
), etc., will change e
o
/e
i
, and hence indicate probable changes in
calibration
5.6.2 Performing a Manual CIC with your 2250 Light
CIC is only available with Logging Software BZ-7133.
Tap the Main Menu icon and select Calibration from the list. Click the CIC tab to view
the various CIC parameters that are available. These include the results of the latest manual
CIC, together with the reference, see Fig.5.9.
The status field at the top of the screen informs you how to perform the CIC.
Press the Start CIC button to start the CIC. After approximately 10 s you will see the result.
Normally, the CIC Reference Ratio is set the very first time a CIC is performed, however, you
should update the CIC Reference Ratio if you change the microphone preamplifier. You do this
by checking the Use as new Reference checkbox.
The CIC Reference Ratio and CIC Ref. Date parameters display the results of the very first
manual CIC, and this will be used as the ‘reference’ for all subsequent CIC Ratio
measurements.
Note: Each microphone in the transducer database has a CIC Reference Ratio.
If the CIC Ratio parameter deviates by more than 0.5 dB from the CIC Reference Ratio , then
there may be a problem, and this should be investigated.
C
m
C
c
C
i
R
1
Preamplifier
Microphone
Cable Generator
g
e
i
e
o
e
o
e
i
C
c
= g
C
m
+ C
i
+ C
c
( )
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