8
LI0010 – 1 October 2015
Electrostatic Calibration of Microphones
The 14AA Electrostatic actuator amplifier can be used for driving an electrostatic actuator for
recording the frequency response of measurement microphones. The measurements can for
example be performed with a general purpose frequency analyzer with built-in signal generator.
The output of the signal generator is connected to the input of the 14AA. The electrostatic
actuator is mounted on the microphone diaphragm and connected to the
AC 800 V DC
output connector. The output signal from the microphone preamplifier is going to the input of the
signal analyzer. The frequency response can then be recorded by a sweep or by a noise excitation
with FFT analysis.
Two different electrostatic actuators are available:
•
1” microphones:
G.R.A.S. RA0015 1’’ Electrostatic Actuator for frequency response calibration.
•
1⁄2”, 1⁄4” and 1/8” microphones:
G.R.A.S. RA0014 1/2’’ Electrostatic Actuator for
frequency response calibration. (Adapters for 1/4” and 1/8’’ microphones are included with the
actuator).
Fig. 9 shows a block diagram showing a setup using the 14AA for frequency calibration with an
electrostatic actuator.
Actuator Supply
14AA
.
Electrostatic Actuator
RA0014
Adapter
Actuator
Calibration Stand
AL0010
Preamplifier
26AB
(inside
calibration
stand)
G.R.A.S.
¼
”-
½
”A
dapter
A
F
00
0
8
Po we r
G.R.A.S.
Actuator Supply
Type 14AA
AC Output
+200VD C
AC Output
Max. 1Vrm s
+800VD C
AC Output
On
GND
AC Input
Overload
G.R.A.S.
RA
0 014
Microphone
for calibration
Frequency calibration equipment
080013
Computer with hardware
and software for signal
generation and signal analysis
Signal generation and analysis
Fig. 9.
Block diagram of a calibration setup using an electrostatic actuator.
