DeltaOHM HD2010UC/A, Руководство по эксплуатации, Страница: 52 / 162

HD2010UC/A
- 52 -
V4.1
E
LECTRIC CALIBRATION
The electric calibration, using the partition of charge injected into the microphone preampli-
fier in “charge amplifier” configuration (Capacitive Transducer Calibration), even if it cannot com-
pletely replace the acoustic calibration, pro-
vides however a useful means to keep under
control the instrument drifts, microphone in-
cluded. The figure on the right shows the
diagram of the CTC technique consisting in
sending an electrical signal to the preampli-
fier through a high stability capacitor, so that
the output signal does not depend only on
amplification, but also on the microphone
capacity. Many of the microphone malfunc-
tions reflect in a capacity drift identifiable by
means of this calibration technique.
The electric calibration uses as a ref-
erence the result of the last acoustic calibra-
tion, and according to it corrects any possible
drift of the instrument.
The electric calibration adjusts the acoustic response of the microphone-sound level meter
chain, both for wideband channels, and for those with a constant percentage bandwidth. In case of
high instrument drift with respect to the previous calibration, it is suggested to carry out an acoustic
calibration and to check the instrument frequency response to verify that there are no other prob-
lems in the measuring chain.
Operating Procedure
Switch on the sound level meter, if it is the case, press STOP to finish the measurement in progress
and make the following procedure:
1. Press PROG and use the DOWN arrow to select "Electric Calibration".
2. Press SELECT to start the function.
3. The inner signal generator will be turned on and the measured output signal will be com-
pared with the one detected in the last acoustic calibration.
The value that appears on the display (51.3dBC in the example below), before starting cali-
bration, is the valued measured by the microphone upon pressure of the PROG key, and is
not relate to the calibration in progress.
ELECTRIC CALIBRATION
Last:2003/01/01 10.00
Calibr. level 94.0dB
Leq dBC
51.3
YES NO
Run calibration
?
4. Press YES to continue and NO to quit.
C
m
C
c
C
f
V
0
Calibration
Signal Source
Transducer
CTC
-A
Charge amplifier
C
b
V
i
V
0
V
i
C
c
C
m
+ C
b
+ C
c
= -
C
b
C
f