G.R.A.S. 41AC-2 LEMO Instruction Manual Download Page 9

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LI0151 – 4 July 2017

Mounting the Upper Housing and the Top Cone

When the microphone has been loosened from the preamplifier, you can 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.

Fig. 5.

Mounting the upper housing and the top cone.

Summary of Contents for 41AC-2 LEMO

Page 1: ...Instruction Manual G R A S 41AC 2 LEMO Outdoor Microphone with RemoteCheck for Community Airport Noise www gras dk LI0151 4 July 2017 ...

Page 2: ... A S Sound Vibration A S http www gras dk Any technical 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 docu...

Page 3: ...3 LI0151 4 July 2017 Contents Introduction 4 Delivered Items 4 Installation 6 System Integration 12 Maintenance 13 Accessories 14 Specifications 14 Calibration Warranty and Service 18 ...

Page 4: ...ons and temperatures for a very long period i e a year or longer It uses a G R A S 40AF S2 1 2 Externally Polarized Free field Microphone High Sensitivity and a G R A S 26AJ 1 2 RemoteCheck Preamplifier with Integrated Connector Important The 40AF S2 microphone and its protective grid have been modified for the 41AC 2 Therefore microphone and grid cannot be replaced by standard items Delivered Ite...

Page 5: ...r the windscreen and thread adapter 2 piece 1 pole mount adapter RA0286 Lower housing Windscreen AM0378 Top cone Preamplfier 26AJ with RemoteCheck Upper housing microphone 40AF S2 Release tube Tripod and thread adapter SK0017 O ring OR2038 Fig 1 The parts of 42AC 2 ...

Page 6: ...g on a 1 pole See Fig 2 and Fig 3 3 The 41AC 2 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 2 lower housing s thread and adaptors for tripod and pole mounting ...

Page 7: ...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: ...using is screwed onto the lower housing Also it makes attachment of the cable to the preamplifier safe 1 Unscrew the nose 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 the p...

Page 9: ... 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: ... 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 wind screen When locked in ...

Page 11: ... 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 the ...

Page 12: ... Therefore neither microphone nor its protective grid can be replaced with standard items Calibration and RemoteCheck Introduction 41AC 2 comes with a RemoteCheck facility that makes it possible to check the integrity of the measurement chain remotely RemoteCheck allows you to send a test signal from analyzer to microphone and record the result It works by applying a precision AC test signal for e...

Page 13: ...ng for example 94 dB SPL Analysis of the Remote Check Signal RemoteCheck verification is based on comparison of historical data from frequent RemoteCheck measurements Depending on the background noise level the expected accuracy of the verifica tion signal will be within 0 15 dB to 0 5 dB If the background noise is about 60 dB SPL the accuracy will be about 0 15 dB if it is 70 dB SPL it will be ab...

Page 14: ...in LEMO 7 pin Cable length in cm AA0020 CLXXXX Specifications 41AC 2 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 200 V Power supply 28 V to 120 V 14 V to 60 V Power consumption 0 7 mA 14 V 2 3 ...

Page 15: ... on background noise 0 15 dB to 0 5 dB 0 V RemoteCheck Fig 8 7 pin LEMO 1B male connector external view on the 41AC 2s preamplifier and output cable The RemoteCheck signal is applied to pin 1 295 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 16: ... 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 and ...

Page 17: ...ence 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 incidence ...

Page 18: ...egligent 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 warran...

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