13
Hardware and Software for Level Calibration
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Power Module
Type 12AQ
Control Box
RA0192
Pistonphone Calibration Stand
AL0017
Pistonphone
Type 42AP
Preamplifier
Type 26AG
Microphone
to be calibrated
G.R.A.S.
Pistonphone
Spring arrangement
Pistonphone Auto-ON/OFF
Static air pressure
Microphone
Definition File
Level Calibration:
- Pistonphone level
and frequency
- Test specifications
(open-circuit sensi-
tivity [max;min])
PXI Cards
Calibration
Software
SW0002
Microphone
Calibration File
Output for
Level Calibration:
Open-circuit
Sensitivity
- Level [mV/Pa]
- Pass/Fail indication
Data Aqui-
sition Card
Signal Conditioning,
Power, and Switching
Control
Card
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G.R.A.S.
RA0192
Active
Actuator
Stand
Polarization
Preamp.
phone
Insert
Piston-
Extended
Range
Frequency
Preamp.
Test
Input
Preamp.
Preamp.
Input Adapter
Signature Series
20
-20
-10
70
-20
30
Overload
Gain in dB
G.R.A.S.
Power Module
Filter
Latch
Overload
Channel 1
Channel 2
Polarization 0V
Preamp. ±15V
Type 12AQ
Remote
Battery
Power
40
10
0
50
60
Ext
Lin
HP
AW
Lin
Ext
Filter
HP
AW
CCP Input
Floating Output
SysCheck
50
60
70
50
60
40
20
30
10
0
-10
Gain in dB
Fig. 7.
Functional block diagram of the 90CA hardware and software for level calibration
The hardware and software for level calibrations are introduced here.
Level Calibration Equipment
• Pistonphone 42AP:
A well-defined sound level reference (sound source); it is
automatically switched on/off via a COM port, and it automatically reads the
static air pressure.
• ½” Preamplifier 26AG
(for ½” microphones) OR (not shown) ¼” Preamplifier
26AN (for ¼” microphones): Both types with an integrated 7-pin LEMO connec-
tor and configured for insert-voltage technique.
• Pistonphone Calibration Stand AL0017:
A fixture for holding the preamplifier
securely in place in the pistonphone and ensuring a stable workspace.
Power, Signal Conditioning, and Switching
• Power Module 12AQ:
A dual-channel power module with supply voltages
and signal conditioning for externally polarized and prepolarized preamplifiers/
condenser microphones.
• Control Box RA0192:
Software-controlled switchbox that automatically
switches the signal path between level calibration and frequency calibration.