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Summary of Contents for GRAS 42AA
- Page 1 G R A S SOUND & VIBRATION Skovlytoften 33, 2840 Holte, Denmark www.gras.dk gras@gras.dk LI0125...
- Page 2 Before shipment, remove the batteries and wrap separately. Assure cautious han- dling during transport. Remove the battery as soon as it is discharged or if the 42AA 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
Otherwise, there is no difference between the two types. Operating Frequency The Pistonphone type 42AA and type 42AA-S1 operates at a frequency of 250Hz. Calibration Level With a microphone inserted in the Pistonhone’s coupler and the Pistonphone and switched on, the nominal calibration level is: •... - Page 5 The Pistonphone is normally delivered with a coupler for calibrating ½-inch microphones. Adapt- ers for calibrating ¼-inch and ⅛-inch microphones are included. A coupler (RA0023) for calibrat- ing 1-inch microphones is also available. Pistonphone Types 42AA/42AA-S1 - Page 5...
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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 Types 42AA/42AA-S1 - Page 6... - Page 7 * 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 0.077 dB. Pistonphone Types 42AA/42AA-S1 - Page 7...
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Page 8: Static-Pressure Corrections
= reference static pressure (1013 hPa) The corrections for ambient static pressure are shown in Fig. 2.2 (see also Appendix A.1 for an extended pressure range). These values should be applied to the nominal Pistonphone level. Pistonphone Types 42AA/42AA-S1 - Page 8... -
Page 9: Barometer
Barometer The Pistonphone is delivered with a small barometer as a standard accessory for use when applying static-pressure corrections. • Type 42AA is delivered with barometer ZC0002K • Type 42AA-S1 is delivered with barometer RA0168 Analogue Barometer ZC0002K (Fig. 2.3) This barometer has the static-pressure corrections printed directly on its scale. -
Page 10: Handling And Operation
20 hours on a new set of batteries. Remove the battery as soon as it is discharged or if the 42AA is stored for a prolonged period of time. Leakage from the batteries may otherwise destroy the electronic components. - Page 11 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-inch microphone adapter inserted in the coupler Pistonphone Types 42AA/42AA-S1 - Page 11...
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Page 12: Inch Microphones
Pistonphone’s nominal sound pressure level L (found on the piston- phone’s calibration chart as “Sound Pressure Level”), the static pressure correction L and the volume correction L , i.e.: Fig. 3.5 ⅛-inch microphone adapter inserted in the coupler Pistonphone Types 42AA/42AA-S1 - Page 12... -
Page 13: 1-Inch Microphones
“Sound Pressure Level”), the static pressure correction L and the volume correction L , i.e.: Fig. 3.6 1-inch and ½-inch couplers The 1-inch coupler is individual calibrated with the pistonphone, and these must be considered as a pair. Pistonphone Types 42AA/42AA-S1 - Page 13... -
Page 14: Calculation Of Microphone Sensitivity
To measure the “Open Circuit Sensitivity” of the microphone (i.e. when the micro- phone’s output is not affected by the load of a preamplifier), a special preamplifier, for example the G.R.A.S. Type 26AG (which has insert voltage calibration capability), should be used. Pistonphone Types 42AA/42AA-S1 - Page 14... -
Page 15: Specifications
Four standard LR6-AA alkaline cells Dimensions: Length: 175 mm (6.89 in) Width: 35 mm (1.38 in) Height: 35 mm (1.38 in) Weight: 325 g (0.7 lbs) Applies only to Pistonphones fitted with a 1-inch microphone coupler RA0023 Pistonphone Types 42AA/42AA-S1 - Page 15... - Page 16 RA0024 (see Fig. 4.1) Octopus coupler (½-inch mics.): RA0072 Fig. 4.1 Two-port Coupler RA0024 shown here with the two phase-matched microphones of an intensity probe Applies only to Pistonphones fitted with a 1-inch microphone coupler RA0023 Pistonphone Types 42AA/42AA-S1 - Page 16...
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Page 17: A Appendix
The influence of air humidity depends on both air temperature and barometric pressure. Fig. A.1 Corrections for static ambient pressure; the small rectangle outlines the range covered by Fig. 2.2 Pistonphone Types 42AA/42AA-S1 - Page 17... - Page 18 The influence of air humidity depends on both air temperature and barometric pressure. ∆L ⋅ C - 0.0064 dB Fig. A.2 Corrections for humidity at different temperatures Manufactured to conform with: CE marking directive: 93/68/EEC WEEE directive: 2002/96/EC RoHS directive: 2002/95/EC Pistonphone Types 42AA/42AA-S1 - Page 18...
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