G.R.A.S. 42AC Instruction Manual Download Page 16

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G.R.A.S. Sound & Vibration

Pistonphone Type 42AC - Page 16

Accessories available:

Adapter for Outdoor Microphone System

Type 41AM:

RA0009

Type 41CN:

RA0041

Adapter for Environmental Microphone

Type 41AL:

RA0010

Coupler for 1

microphones:

RA0023

Coupler for ½

microphones:

RA0048

Adapter for hydrophone couplers:

GR0398

Digital precision barometer:

RA0168

Two-port high-pressure

calibration coupler:

RA0042 (see Fig. 4.1)

Octopus coupler (½

mics.):

RA0072

Applies only to Pistonphones fitted with a 1

microphone coupler RA0023

Fig. 4.1 Two-port Coupler RA0042 shown

here with the two phase-matched

microphones of an intensity probe

WEEE directive:
2002/96/EC

CE marking directive:

93/68/EEC

Manufactured to conform with:

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.

Summary of Contents for 42AC

Page 1: ...Instruction Manual www gras dk LI0126 4 July 2013 G R A S 42AC 42AC S2 Pistonphone ...

Page 2: ...ilable by G R A S is the copyrighted work of G R A S and is owned by G R A S The content in this document is subject to change without notice G R A S Sound Vibration A S is not liable or responsible for any errors or inaccuracies that may appear in this document Trademarks Product names mentioned in this document may be trademarks or registered trademarks of their respective companies and are here...

Page 3: ... Operation 9 3 1 Shipment and Transport 9 3 2 Batteries 9 3 3 Calibrating Microphones 9 3 3 1 Microphone Size 9 3 3 2 Microphones 9 3 3 3 Microphones 10 3 3 4 Microphones 11 3 3 5 1 Microphones 12 3 4 Calculation of Microphone Sensitivity 13 3 5 Calibrating Hydrophones 13 3 5 1 Calibrating Hydrophone Type 10CT 14 4 Specifications 15 A Appendix 17 A 1 Corrections for Static Ambient Pressure 17 A 2 ...

Page 4: ...evel is 134dB1 re 20µPa 125 4dBA re 20µPa with A weighting applied At a static ambient pressure of 1013hPa no further correction factors need be applied An indi vidual calibration chart is delivered with each Pistonphone The Pistonphone is an extremely stable laboratory standard sound source which can also be used for field calibrations it retains its high accuracy even under hostile environmental...

Page 5: ...constant sound pressure level on the diaphragm of the microphone The Type 42AC is delivered with a 1 2 coupler1 RA0048 for calibrating 1 2 microphones directly The Type 42AC S2 is delivered with a 1 coupler1 RA0023 for calibrating 1 micro phones directly Adaptors for calibrating and microphones are included 1 The coupler is individually calibrated with the pistonphone and these must be considered ...

Page 6: ...re determined by the physical dimensions of the pistons and the cam disc the ambi ent pressure refers in most cases to the barometric pressure of the atmosphere 2 2 Volume Corrections The volume of the coupler is defined partly by the dimensions of the coupler itself and partly the effective load volume of the microphone The effective load volume of the microphone is sum of the equivalent volume a...

Page 7: ... The equivalent volume uncertainty is 7mm3 The correction uncertainty is 0 004dB No equivalent volume correction is needed for calibration of microphones G R A S type 40BD 40BE 40BF 40BP using the adaptor RA0049 nor 1 microphone G R A S type 40EN using the adaptor RA0023 When calibrating 1 8 microphones G R A S type 40DD 40DP using the adaptor RA0069 the equivalent volume correction is 19mm3 and r...

Page 8: ...elivered with a small barometer ZC0003K as a standard accessory for use when applying static pressure corrections Analogue Barometer ZC0003K Fig 2 3 This barometer has the static pressure corrections printed directly on its scale Digital Barometer RA0168 Fig 2 4 This has an LCD which can display via a toggle button either the static pressure correction e g 0 13dB or the ambient static pressure e g...

Page 9: ...rs 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 3 3 Calibrating Microphones 3 3 1 Microphone Size The Pistonphone is normally delivered ready to calibrate microphones For and microphones special adapters are included and for 1 microphones a ...

Page 10: ...subjected to a sound pressure level LC given as the sum of the Pistonphone s nominal sound pressure level LN the static pressure cor rection LB and the volume correction LV i e Fig 3 3 microphone inserted in the coupler 3 3 3 Microphones To calibrate a measurement microphone first loosen the microphone retention collar as shown in Fig 3 2 Then insert the microphone adapter RA0049 into the coupler ...

Page 11: ...n collar so that the adapter is held firmly in place Insert the microphone into the adapter Switch the Pistonphone on via the on off I 0 button The LED above the on off button is a dual colour LED for showing red or green The LED shows green if the Pistonphone is operating properly at the specified frequency If the LED shows red or flashing red the Pistonphone is not operating at the specified fre...

Page 12: ...s operating properly at the specified frequency 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 Wait approximately for 15 seconds for the static pressure in both the Pistonphone and the microphone to stabilise and for the microphone itself to stabilise within the coupler The static pressure within ...

Page 13: ...esent ative or send an email to support gras dk The Adapter GR0398 shown in Fig 3 7 is available for hydrophone couplers Unscrew the coupler from the Pistonphone body The pistons and retention spring shown in Fig 2 1 are protected so there is no risk of accidentally damaging these parts when removing the coupler Screw the Adapter GR0398 onto the Pistonphone body The Pistonphone is now ready to acc...

Page 14: ...ed use the refer ence microphone to measure the SPL applied to the hydrophone 3 future calibration checks knowing the SPL applied to the given hydro phone Fig 3 9 shows the three steps of calibrating a given Hydrophone Type 10CT In step 1 check the reference microphone in the normal way as described in section 3 2 2 In step 2 replace the pistonphones coupler with the RA0043 Push both reference mic...

Page 15: ...ure 1 mic 0 2dB Frequency 250Hz 0 5 Distortion 1 5 Nominal effective coupler volume 12530mm3 including effective load volume of microphone type 40AG or type 40EN Temperature range 10 C to 55 C batteries permitting Batteries Four standard LR6 AA alkaline cells Dimensions Length 175mm 6 89in Width 35mm 1 38in Height 35mm 1 38in Weight 325g 0 7lbs Accessories included Adapter for microphones RA0049 A...

Page 16: ...wo port high pressure calibration coupler RA0042 see Fig 4 1 Octopus coupler mics RA0072 1 Applies only to Pistonphones fitted with a 1 microphone coupler RA0023 Fig 4 1 Two port Coupler RA0042 shown here with the two phase matched microphones of an intensity probe WEEE directive 2002 96 EC CE marking directive 93 68 EEC Manufactured to conform with RoHS directive 2002 95 EC G R A S Sound Vibratio...

Page 17: ...red by Fig 2 2 A 2 Corrections for Humidity For highly precise calibrations in accordance with IEC Standard 942 Class 0 it will be neces sary to correct for the influence of air humidity The influence of air humidity depends on both air temperature and barometric pressure The curves in Fig A 2 show corrections C which account for the effects of both temperature and humidity when the ambient pressu...

Page 18: ...18 The correction LH has to be added to the other correction factors in equations 4 5 6 and 7 The value C together with the actual value of the barometric pressure PA are used as follows to calculate the actual correction humidity LH C 0 0064dB Pr Pa 9 ...

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