BRUEL & KJAER 2204 User Manual

dB
+1
0
-1
-2
-3
~
/
-10
0
10 20 30
0 20
40 60 80
r--.....
~"-
40
50
100
120
. 140 •F
141669
Fig. 6 . .f.. Amplification versus temperature for the amplifier.
Calibration Signal.
The calibration signal for the amplifiers and meter circuit is obtained from a
stabilized 1 kHz supply used also for the microphone polarization voltage.
The signal is well stabilized both for variations in battery voltage and
for changes in temperature. Fig. 5.5 shows the variation in signal voltage with
temperature. When the calibration signal increases due to temperature, the
sensitivity of the input amplifier will be reduced when calibration is carried
out. At the same time the sensitivity of the microphone increases due to in-
crease in polarization voltage, so that the net result is a very slight or no
change in overall sensitivity of the instrument.
dB
1.2
1.0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-o.&
-0.8
-1.0
-1.2
-10
0
--
~
~
~
~
-----
~
--
10
20
30
40
50
60 °C
(6(69,.
Fig. 5.5. The variation in calibration voltage as a function of temperature.
Power Supply.
Because of possible variations in battery voltage a stabilization circuit is
inserted before the 1 kHz oscillator which transforms the DC voltage from
the batteries into the required voltage levels.
29

BRUEL & KJAER 2204 Specifications

General

Brand	BRUEL & KJAER
Model	2204
Category	Measuring Instruments
Language	English