G.R.A.S. Sound & Vibration
Single-channel Low-noise Measuring System consisting of: Type 40HT and Type 12HF - Page 12
Fig. 3.2 Pistonphone fitted with Coupler RA0090 and the microphone
inserted into the Coupler
6. Mount the microphone of the Type 40HT in the Coupler as shown in Fig. 3.2 and switch the
Pistonphone on.
7. Adjust the analyser to indicate 94 dB* re. 20 μPa.
3.2 Measurements
1. Assemble the system as shown in Fig. 1.3.
2. Connect the output from the Power Module to an analyser.
3. Switch both Power Module and analyser on.
4. Calibrate the set up via one of the methods described in section 3.1.
5. Select which microphone operation to use via the switch on the front panel of the Type
12HF marked
Pressure
/
Free Field
.
At this point you can make your measurements but keep an eye on the overload warning LEDs
to avoid overloading the system and invalidating the measurements.
* Plus any corrections for barometric pressure. See pistonphone manual.
