G.R.A.S. Type 12HF Instruction Manual Download Page 2 | Manualshive

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Revision 7 September 2012

Single-channel

Low-noise Measuring System

consisting of:

½-inch Low-noise Level Microphone System Type 40HT

Power Module Type 12HF

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Summary of Contents for Type 12HF

Page 1: ...oise Measuring System consisting of inch Low noise Level Microphone System Type 40HT 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 To Analyser Type 12HF Type 40HT ...

Page 2: ...Revision 7 September 2012 Single channel Low noise Measuring System consisting of inch Low noise Level Microphone System Type 40HT Power Module Type 12HF ...

Page 3: ...ifier Type 26HG 5 2 Power Module Type 12HF 7 2 1 Front Panel 7 2 2 Rear Panel 8 2 3 Battery Pack 9 3 Operation 10 3 1 Calibration 10 Based on System Sensitivity 10 Pistonphone 10 3 2 Measurements 11 4 Specifications 12 4 1 inch Low noise Microphone System Type 40HT 12 4 2 Single channel Power module Type 12HF separate order 12 4 3 Common 13 ...

Page 4: ...er Unit Type 26HT with two built in compensation filters and an overload warning LED To complete the system a special single or 10 channel power module is required and is avail able from G R A S i e Type 12HF for single channel measurements see Fig 1 2 left Or Type 12HM for multi channel 1 to 10 measurements see Fig 1 2 right The chosen power module provides all necessary voltages for powering the...

Page 5: ...and wide frequency range 1 2 Gain and Filter Unit Type 26HT The body of the Unit 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 Gain and Filter Unit Type 26HT The two compensation filters give the system two parallel outputs which correspond to a linear pressure frequency respo...

Page 6: ...se free field corrections are for various angles of incidence Fig 1 6 shows for a complete low noise measuring system a typical noise floor in octave bands for both the linear and A weighted cases 1 3 Preamplifier Type 26HG Similar to the standard G R A S Type 26AC but with 40GΩ input impedance to enable low level and low frequency noise measurements The preamplifier has an integrated 3 metre ligh...

Page 7: ...tions for various angles of incidence on the inch Microphone Type 40AH Fig 1 6 Typical noise floor of Type 40HT for system and microphone Shown in octave bands for both the linear and A weighted cases 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 ...

Page 8: ...he 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 volt age is too low Two position switch for selecting frequency response Pressure microphone operation or Free Field microphone operation Pressu...

Page 9: ... The rear panel 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 ...

Page 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 ...

Page 11: ... Module and analyser on 3 Adjust the analyser to indicate 94dB re 20μPa for an RMS input of S volts where S is the system sensitivity of the Type 40HT as quoted on the calibration chart 3 1 2 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 40HT Note a Pistonphone fitted with a normal inc...

Page 12: ...urements 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...

Page 13: ...Hz 20kHz 2 0dB 3 0dB Nominal 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 4 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 inte...

Page 14: ... 3 Common Temperature range 20 C to 60 C Accessories available 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 RA0096 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 R...

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