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Summary of Contents for G.R.A.S. 42AC
- Page 1 Instruction Manual G.R.A.S. 42AC/42AC-S2 Pistonphone www.gras.dk LI0126 – 4 July 2013...
- Page 2 Before shipment, remove the batteries and wrap separately. Assure cautious handling during transport. Remove the battery as soon as it is discharged or if the 42AC is stored for a prolonged period of time. Leakage from the batteries may otherwise destroy the electronic components.
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Page 3: Table Of Contents
G.R.A.S. Sound & Vibration CONTENTS General Description ..........4 Operating Frequency . -
Page 4: General Description
G.R.A.S. Sound & Vibration General Description The G.R.A.S. Pistonphone Type 42AC (Fig. 1.1) is a battery-operated, precision sound source for accurate and reliable calibration of measurement microphones, sound level meters and other sound measuring equipment. • Type 42AC includes ½" microphone coupler. - Page 5 The Type 42AC is delivered with a 1/2" coupler (RA0048) for calibrating 1/2" microphones directly. The Type 42AC-S2 is delivered with a 1" coupler (RA0023) for calibrating 1" micro- phones directly. Adaptors for calibrating ¼" and ½" microphones are included.
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Page 6: Theory
Since the grid and equivalent volumes can vary slightly from one type of microphone to another, the total volume of the coupler will, accordingly, also vary slightly. Pistonphone Type 42AC - Page 6... -
Page 7: Static-Pressure Corrections
* The G.R.A.S. Microphone Type 40AG is equivalent to the Brüel & Kjær Type 4134 and the volume correction for these are 0 dB. As a matter of interest, the volume correction for a G.R.A.S. Type 40AU and a Brüel & Kjær Type 4180 is 0.095 dB. Pistonphone Type 42AC - Page 7... -
Page 8: Barometer
(e.g. – 0.13 dB) or the ambient static pressure (e.g. 997 hPa). It runs on standard 9 V battery which can be accessed by removing the back plate which is held in place by four screws. On/Off switch Toggle button Fig. 2.3 Barometer ZC0003K Fig. 2.4 Barometer RA0168 Pistonphone Type 42AC - Page 8... -
Page 9: Handling And Operation
The Pistonphone can operate continuously for about 20 hours on a new set of batteries. Remove the battery as soon as it is discharged or if the 42AC is stored for a prolonged period of time. Leakage from the batteries may otherwise destroy the electronic components. -
Page 10: Microphones
If the LED shows red or flashing red, the Pistonphone is not operating at the specified frequency and the batteries should be changed (see section 3.2). Fig. 3.4 ¼" microphone adapter inserted in the coupler Pistonphone Type 42AC - Page 10... -
Page 11: Microphones
Pistonphone’s nominal sound pressure level L N, the static pressure cor- rection L B and the volume correction L V, i.e.: Fig. 3.5 ⅛" microphone adapter inserted in the coupler Pistonphone Type 42AC - Page 11... -
Page 12: 1" Microphones
Pistonphone’s nominal sound pressure level L N, the static pressure cor- rection L B and the volume correction L V, i.e.: Fig. 3.6 1" and ½" couplers The 1" coupler is individual calibrated with the pistonphone, and these must be considered as a pair Pistonphone Type 42AC - Page 12... -
Page 13: Calculation Of Microphone Sensitivity
(see section 3.1). Wait approximately for 15 seconds for the static pressure in Pistonphone to stabilise and for the hydrophone to stabilise within its coupler. Fig. 3.7 Adapter GR0398 for hydro- phone couplers Pistonphone Type 42AC - Page 13... -
Page 14: Calibrating Hydrophone Type 10Ct
In step 3, the reference microphone is not needed but seal the microphone hole as shown (push the plug in all the way) when making future calibrations of the given hydrophone. The hydro- phone will be subjected to the same SPL as measured in step 2. Pistonphone Type 42AC - Page 14... -
Page 15: Specifications
Adapter for ¼" microphones: RA0049 Adapter for ⅛" microphones: RA0069 Barometer: ZC0003K Coupler for ½" microphones RA0048 Coupler for 1" microphones RA0023 Four LR6-AA alkaline cells: EL0001 Applies only for 42AC Applies only for 42AC-S2 Pistonphone Type 42AC - Page 15... - Page 16 CE marking directive: 93/68/EEC WEEE directive: 2002/96/EC RoHS directive: 2002/95/EC G.R.A.S. Sound & Vibration continually strives to improve the quality of our products for our customers; therefore, the specifications and accessories are subject to change. Pistonphone Type 42AC - Page 16...
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Page 17: A Appendix
The curves in Fig. A.2 show corrections (C) which account for the effects of both temperature and humidity when the ambient pressure equals the reference pressure P (101.3 kPa). Fig. A.2 Corrections for temperature humidity Pistonphone Type 42AC - Page 17... - Page 18 ∆L ⋅ C ⋅ + 0.0064 dB The correction ∆L has to be added to the other correction factors in equations 4, 5, 6 and 7. Pistonphone Type 42AC - Page 18...
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