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G.R.A.S. 40HH, Инструкция по эксплуатации

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G.R.A.S.  SOUND & VIBRATION

Single-channel Low-noise Measuring System consisting of: Type 40HH and Type 12HF - Page  12

  Fig. 3.2  Pistonphone fitted with Coupler RA0090 and the 

 

     microphone 

inserted 

into 

the 

Coupler

 7. Adjust the analyser to indicate 94 dB* re. 20 μPa.

3.3 

Frequency Response Calibration

The frequency response of the microphone has been factory-calibrated in a free field (anechoic 

chamber) by comparison with a reference microphone. 

Due to the high sensitivity of the microphone and undamped microphone resonance, the micro-

phone response around the resonance frequency may be influenced by the loading of the 

microphone diaphragm from the electrosatic actuator.

*  Plus any corrections for barometric pressure. See pistonphone manual.

Содержание 40HH

Страница 1: ...annel Low noise Measuring System consisting of inch Low noise Level Microphone System Type 40HH and Power Module Type 12HF G R A S Sound Vibration Skovlytoften 33 2840 Holte Denmark Tel 45 45 66 40 46 Fax 45 45 66 40 47 12HF 40HH ...

Страница 2: ...Revision 17 September 2017 Single channel Low noise Measuring System consisting of Low noise Level Microphone System Type 40HH Power Module Type 12HF ...

Страница 3: ... 7 2 2 Rear Panel 8 2 3 Battery Pack 9 3 Calibration 10 3 1 Based on System Sensitivity 10 3 2 Level Calibratinon using a Pistonphone 10 3 3 Frequency Response Calibratoin 11 4 Measurements 11 5 Specifications 12 5 1 Low noise Microphone System Type 40HH 12 5 2 Single channel Power module Type 12HF separate order 12 5 3 Common 13 6 What to Order 14 ...

Страница 4: ...ial high sensitive microphone It is externally polarized with a spe cially reduced inherent noise floor in order to achieve a high dynamic range and wide frequency range 1 2 Preamplifier Type 26HH The body of the Preamplifier has an overload warning LED Fig 1 1 which is repeated on the front panel of the chosen power module see Fig 2 1 The signal of the microphone is amplified by 20dB in the Pream...

Страница 5: ... this document shown here with Tripod and Tripod Adapter both available from G R A S Fig 1 2 Power modules available from G R A S for Type 40HH Left Single channel Power Module Type 12HF Right 10 Channel Module Type 12HM Tripod Adapter RA0093 Tripod AL0006 Low noise Level Microphone System Type 40HH Single or 10 chan nel power module here single chan nel Power Module Type 12HF ...

Страница 6: ...pe 12HF Page 6 Fig 1 4 Typical frequency response curves of Type 40HH Fig 1 5 Free field corrections for various angles of incidence on the Microphone Type 40AH 100kHz 10kHz 1kHz 100Hz Decibels re level at 250 Hz 6 4 2 0 2 4 6 8 10 180º Random incidence 150º 120º 0º 30º 60º 90º 0º 90º 120º 8 14 12 ...

Страница 7: ...TION Single channel Low noise Measuring System consisting of Type 40HH and Type 12HF Page 7 Fig 1 6 Typical noise floor of Type 40HH for system and microphone Shown in octave bands for both the linear and A weighted cases ...

Страница 8: ...e following features see Fig 2 1 Power switch with two LEDs green OK red Batt Low If the power supply is correct the green LED lights up If the red LED lights up either the batteries are low and should be changed see section 2 3 or the external DC supply voltage is too low Two position switch for selecting frequency response Pressure microphone operation or Free Field microphone operation Pressure...

Страница 9: ...el has the following features see Fig 2 3 Twist release holder for 315mA fast blow fuse Input socket for an external voltage supply of 6V 20V DC centre pin terminal Use the Mains line Adapter AB0010 supplied with the Type 12HF Locking screw Unscrew to remove base plate and gain access to the battery pack see section 2 3 Fig 2 2 7 pin LEMO EGA 307 1B input socket external view Fig 2 3 Rear panel of...

Страница 10: ...ing screw on the rear panel Fig 2 3 and slide the base plate off towards the rear Pull out the battery pack See Fig 2 4 The battery pack consist of a battery holder and 4xLR14 C standard alkaline cells When replacing the batteries replace all of them making sure that the polarity is as indicated on the battery holder Fig 2 4 Showing the battery pack of the Power Module Type 12HF ...

Страница 11: ...Pa for an RMS input of S volts where S is the system sensitivity of the Type 40HH as quoted on the calibration chart 3 2 Level Calibration using a Pistonphone A Pistonphone Type 42AA fitted with a Coupler RA0090 both available from G R A S can be used to produce 94dB re 20μPa on the microphone of the Type 40HH Note a Pistonphone fitted with a normal coupler cannot be used because this will overloa...

Страница 12: ...ncy Response Calibration The frequency response of the microphone has been factory calibrated in a free field anechoic chamber by comparison with a reference microphone Due to the high sensitivity of the microphone and undamped microphone resonance the micro phone response around the resonance frequency may be influenced by the loading of the microphone diaphragm from the electrosatic actuator Plu...

Страница 13: ...ule 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 mea...

Страница 14: ...inal sensitivity System 800mV Pa 2dB Microphone polarization voltage 200V Dynamic range Upper limit 113dB re 20µPa Lower limit 6 5dBA re 20µPa inherent noise Microphone capacitance 20pF 5 2 Single channel Power module Type 12HF separate order Input channel 7 pin LEMO EGA 1B connector Outputs channel BNC socket Output impedance 30Ω Polarization voltage 200V Power supply Internal 6V from 4xLR14 C st...

Страница 15: ...ne Adapter AB0010 Optional Accessories Power module 1 ch Type 12HF Power module 10 ch Type 12HM Windscreens set of 5 AM0069 Pistonphone Type 42AA Pistonphone Coupler RA0090 for 94dB re 20µPa Tripod AL0006 Tripod Adapter RA0093 3m Ext cable AA0046 10m Ext cable AA0047 30m Ext cable AA0048 WEEE directive 2002 96 EC CE marking directive 93 68 EEC Manufactured to conform with RoHS directive 2002 95 EC...

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