Typical applications and use
- Wind-induced noise on ground and airbornevehicles
- Acoustic radiation from surfaces
- Noise tests in wind tunnels
- Comparing the external noise on a moving vehicle with its internal noise
Together with any of the G.R.A.S. mountings, the profile of the surface microphone is just 2.8 mm. Its wide audio frequency range extends from 20 Hz to 20 kHz and its large dynamic is from below 32 dBA to 136 dB.
It has an integrated CCP preamplifier with a built-in TEDS chip which enables the Surface Microphone as a whole to be programmed as a complete single unit.
Close manufacturing tolerances together with the advantages of the TEDS chip, provide the G.R.A.S. 40PS with a high degree of interchangeability; a major advantage which excludes accounting for individual characteristics.
The G.R.A.S. 40PS requires a constant-current power supply such as the G.R.A.S. CCP Supply G.R.A.S.12AL, or any other compatible constant-current power supply.
The G.R.A.S. 40PS is both stable and robust and has an integrated 1.5 m coaxial cable with a microdot connector. It is delivered with a supple detachable silicon-rubber fairing.
Because of its lightness, the G.R.A.S. 40PS can be readily mounted with its fairing on surfaces using a double-sided adhesive pad contributes very little mass to thin plates.
Pressure equalisation is via a vent placed at the front of the microphone just by the side of its diaphragm. This is important especially when used on aircraftand on road vehicles in mountainous country.
The G.R.A.S. 40PS can be easily calibrated using a G.R.A.S. Pistonphone and a special Adapter RA0145.
All G.R.A.S. Surface Microphones are individually checked and calibrated before leaving the factory.
An individual calibration chart is supplied with each microphone and also includes an individual pressure frequency response.
|Frequency range (±1 dB)||Hz||100 to 3 k|
|Frequency range (±3 dB)||Hz||20 to 10 k|
|Dynamic range lower limit (microphone thermal noise)||dB(A)||<32|
|Dynamic range upper limit with G.R.A.S. CCP preamplifier||dB||136|
|Set sensitivity @ 250 Hz (±2 dB)||mV/Pa||5|
|Power supply (Constant Current Power)||mA||2 to 10|
|Temperature range, operation||°C / °F||-10 to 50 / 14 to 122|
|Temperature range, storage||°C / °F||-40 to 85 / -40 to 185|
|TEDS UTID (IEEE 1451.4)||27 v. 1.0|
|Connector type||Microdot 10/32|
|CE/RoHS compliant/WEEE registered||Yes / Yes / Yes|
|Weight||g / oz||3 / 0.101|
Typical pressure frequency response
|G.R.A.S. GR0933||Top adhesive pad 0.5 mm (pre-cut, single-sided)|
|G.R.A.S. GR0934||Base adhesive pad 0.13 mm (pre-cut, double-sided)|
|G.R.A.S. MI0031||Cleaning tissue|
|G.R.A.S. AE0046||Adapter BNC male to microdot female
|G.R.A.S. RA0147||Aluminum mounting plate|
|G.R.A.S. 42AA/G.R.A.S. 42AP||Pistonphones|
|G.R.A.S. 12AL||CCP supply|
|G.R.A.S. RA0145||Calibration adapter for Pistonphone|