G.R.A.S. 41AC-4 LEMO Instruction Manual Download Page 16

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LI0171 – 18 February 2015

Frequency [Hz]

Amplit

e (dB)

1000

10000

Acceptance limits for deviations of directional response

41AC w. windscreen

0º incidence Lim dev ±90º

0° incidence
90° incidence
Lim w. uncertanty ±90º
Lim dev ±90º

±90° Directional Response Measurements

0° and 90° Incidence

0° incidence

90° incidence

IEC 61672-1 tolerance

IEC 61672-1 acccep. limit

Fig. 12.

±90˚ directional response at 0° and 90° incidence.

1000

10000

Acceptance limits for deviations of directional response

41AC w. windscreen

0º incidence Lim dev ±150º

0° incidence
90° incidence
Lim w. uncertanty ±150º
Lim dev ±150º

Frequency [Hz]

Amplit

e (dB)

±150° Directional Response Measurements

0° and 90° Incidence

0° incidence

90° incidence

IEC 61672-1 tolerance

IEC 61672-1 acccept. limit

Fig. 13.

±150˚ directional response at 0° and 90° incidence.

Summary of Contents for 41AC-4 LEMO

Page 1: ...Instruction Manual G R A S 41AC 4 LEMO Outdoor Microphone for Community and Airport Noise 0 V pol www gras dk LI0171 18 February 2015 ...

Page 2: ...ical documentation that is made available 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 Any product names mentioned in this document may be trademarks or registered trademarks of ...

Page 3: ...3 LI0171 18 February 2015 Contents Introduction 4 Delivered Items 4 Installation 6 System Integration 12 Maintenance 12 Accessories 13 Specifications 13 Calibration Warranty and Service 17 ...

Page 4: ... longer It uses a G R A S 40AE S2 1 2 Prepolarized Free field Microphone High Sensitivity and a G R A S 26AK 1 2 Standard Preamplifier with LEMO Connector It is designed for use with a Sound Level Meter with LEMO connector and power supply and 0 V polarization voltage Important The 40AE S2 microphone and its protective grid have been modified for the 41AC 4 Therefore microphone and grid cannot be ...

Page 5: ...cept for the windscreen and thread adapter 2 piece 1 pole mount adapter RA0286 Lower housing Windscreen AM0378 Top cone Preamplifier 26AK Upper housing microphone 40AE S2 Release tube GR1794 Tripod and thread adapter SK0017 O ring OR2038 Fig 1 The parts of 42AC 4 ...

Page 6: ...ing on a 1 pole See Fig 2 and Fig 3 3 The 41AC 4 s housing is attached to the mount ing fittings with a M18 x 1 5 thread Two piece pipe adapter with 1 pipe thread ISO 228 1 G1 M18 x 1 5 GR1096 Tripod thread adapter with SK0017 1 4 threaded bushing Tripod thread adapter with 3 8 thread without bushing Fig 2 The 41AC 4 lower housing s thread and adaptors for tripod and pole mounting ...

Page 7: ...at it is protected from dirt and moisture 3 Slide the microphone cable through the adapter and through the lower housing and screw the housing onto the pole mount adapter 4 Ensure that the lower housing is properly fastened to the pole mount adapter 2 3 1 2 3 1 1 2 3 4 Fig 3 Attaching the lower part of the housing to the pole mount adapter ...

Page 8: ...r housing is screwed onto the lower housing Also it makes attachment of the cable to the preamplifier safe 1 Unscrew the top cone 2 Set it aside Make sure it is protected from dirt and moisture 3 Loosen the microphone housing by half a turn Hold at the preamplifier connector and the lower part of the microphone body while turning Important Make sure to loosen the microphone housing and not only th...

Page 9: ...an safely mount the upper housing onto the lower housing and subsequently mount the top cone 1 Screw the upper part of the housing onto the lower part 2 Fasten the microphone by turning it clockwise 3 Screw on the top cone 4 Ensure that the top cone is properly fastened 1 2 3 4 6 5 6 5 Fig 5 Mounting the upper housing and the top cone ...

Page 10: ...en is pushed as far down as it will go it will be kept in place by a locking groove Because of this it cannot be dislocated unintentionally and incorrect measurements due to an incorrectly positioned windscreen are avoided 1 Slide the tube down over the top cone 2 Ensure that the tube is pushed as far down as it will go 1 2 End stop Locking groove Top of microphone diaphragm Fig 6 Mounting the win...

Page 11: ... a piece of hard plastic Caution Do NOT pull at the foam as this could cause it to deform or loosen it from the tube Disconnecting Preamplifier and Cable When disconnecting the cable from the preamplifier you must push the black release tube upwards This will cause the LEMO connector s locks to release 1 Unscrew the top cone see Fig 7 a2 2 Push the black release tube upwards See Fig 7b 1 3 Pull th...

Page 12: ...designed specifically for the 41AC 4 Only the 40AE S2 will ensure the stated measurement results and water protection Therefore neither microphone nor its protective grid can be replaced with standard items Verification and Calibration An acoustic in situ verification or a calibration in a laboratory with a pistonphone or a sound calibrator requires that windscreen and top cone are dismantled How ...

Page 13: ...MO 7 pin Cable length in cm AA0020 CLXXXX Specifications 41AC 4 Dynamic range lower limit microphone thermal noise 17 dB A Dynamic range upper limit with 28 V 14 V supply 138 dB Dynamic range upper limit with 120 V 60 V supply 144 dB Set sensitivity 250 Hz 2 dB 50 mV Pa Compliance IEC 61672 1 Polarization voltage 0 V Power supply 28 V to 120 V 14 V to 60 V Power consumption 0 7 mA 14 V 2 3 mA 60 V...

Page 14: ...7 pin LEMO 1B male connector external view on the 41AC 4s preamplifier and output cable 295 mm 112 3 in 343 mm 131 2 in 12 mm 1 2 in 1 pipe thread ISO 228 1 G1 Fig 9 When mounted on a pipe the top of the 41AC will be elevated 343 mm above the pipe ...

Page 15: ...al Frequency Response Frequency Hz Amplitude dB IEC 61672 1 accept limit IEC 61672 1 accept limit Fig 10 Typical frequency response 0 0 5 1 1 5 2 2 5 3 3 5 4 4 5 5 1000 10000 Acceptance limits for deviations of directional response 41AC w windscreen 0º incidencs Lim dev 30º 0 incidence 90 incidence Lim w uncertanty 30º Lim dev 30º Frequency Hz Amplitude dB 30 Directional Response Measurements 0 an...

Page 16: ...idence IEC 61672 1 tolerance IEC 61672 1 acccep limit Fig 12 90 directional response at 0 and 90 incidence 0 2 4 6 8 10 12 14 16 18 20 1000 10000 Acceptance limits for deviations of directional response 41AC w windscreen 0º incidence Lim dev 150º 0 incidence 90 incidence Lim w uncertanty 150º Lim dev 150º Frequency Hz Amplitude dB 150 Directional Response Measurements 0 and 90 Incidence 0 incidenc...

Page 17: ...o negligent use an incorrect power supply or an incorrect connection to the equipment Service and Repairs All repairs are made at G R A S International Support Center located in Denmark Our Support Center is equipped with the newest test equipment and staffed with dedicated and highly skilled engineers Upon request we make cost estimates based on fixed repair categories If a product covered by war...

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