Typical applications and use
- Acoustic-impedance measurements
- Exhaust-system measurements
- Near-field measurements
- Measurements at high temperatures
- Pressure-distribution measurements in small enclosures
The G.R.A.S. 40SC is constructed with detachable stainless-steel probes tubes which guide the acoustic signal to a prepolarised microphone inside the housing of the 40SC. After being sensed by the microphone, the acoustic signal is passed on to an impedance-matching wave guide which eliminates unwanted internal reflections. The result is a smooth frequency-response ranging from 2 Hz up to 20 kHz. The internal microphone is connectedto an CCP preamplifier with a high dynamic range; ensuring a measurement range from approximately 40 dB to 160 dB re. 20 μ Pa.
The integrated BNC socket is for drawing power from, and delivering the signal to, a constant-current power supply, e.g. the G.R.A.S. 12AL CCP Supply, or any other compatible constant-current power supply.
The CCP Probe Microphone 40SC is internally compensated to equalize the internal pressure of the microphone with the static pressure at the probe’s tip . The static pressure within the 40SC will therefore adjust itself to the static pressure existing at the probe’s tip; which it does with a time constant of approximately 0.1 s.
The 40SC can be used with various probe lengths and is delivered with four standard probe lengths, i.e.: 20 mm, 40 mm, 80 mm and 160 mm. Intermediate lengths can be made by cutting these standard lengths. Also, the stainless steel tubes can be bent to a radius as low as 5 mm without downgrading the system’s acoustics. A flexible probe tube is also provided for use in measurements where stiff stainless-steel tubes are not practical. This does, however, slightly downgrade the system’s acoustic performance.
The right angled design of the 40SC makes it particularly well suited for measurements on exhaust-gas systems and other machinery in general as well as for scanning vibrating surfaces such as loudspeaker diaphragms and cabinets.
The compact size, low weight and all-stainless-steel construction of the 40SC make it robust, easy to handle and easy to mount.
|Frequency range (±3 dB)||Hz||2 to 8 k|
|Dynamic range lower limit (microphone thermal noise)||dB(A)||40|
|Dynamic range upper limit||dB||>160|
|Set sensitivity @ 250 Hz (±2 dB)||mV/Pa||3|
|Polarization voltage||V||0 V / CCP|
|Power supply (Constant Current Power)||mA||2 to 20|
|Temperature range, operation||°C / °F||-25 to 700 / -13 to 1292|
|Temperature range, storage||°C / °F||-40 to 85 / -40 to 185|
|Temperature range with G.R.A.S. preamplifier, operation||°C / °F||-25 to 70 / -13 to 158|
|CE/RoHS compliant/WEEE registered||Yes/Yes/Yes|
|Weight||g / oz||40 / 1.4110|
Pressure-equalization time constant: Internal to tip static pressure: typically 0.1 s
Typical frequency response
|G.R.A.S. AA0034||2 m BNC - BNC Cable|
|G.R.A.S. GR0265||Pistonphone adaptor for 1.25 mm|
|G.R.A.S. GR0266||Pistonphone adaptor for 1.6 mm|
|G.R.A.S. GR0267||Heatsink and tool|
|G.R.A.S. GR0275||Calibration coupler|
|G.R.A.S. GR0263||1.3 mm pin for calibration coupler|
|G.R.A.S. GR0264||1.6 mm pin for calibration coupler|
|G.R.A.S. YY0004||Pair of pliers|
|G.R.A.S. MI0016||Silicone grease|
|G.R.A.S. EK0018||Teflon tubing (L: 0.5 m Dia: 1.6 mm)|
|G.R.A.S. GR0258||20 mm Probe tube|
|G.R.A.S. GR0259||40 mm Probe tube|
|G.R.A.S. GR0260||80 mm Probe tube|
|G.R.A.S. GR0261||160 mm Probe tube|
|G.R.A.S. GR0401||Flexible Probe tube|
|G.R.A.S. 12AL||Power module|