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

Instruction Manual

G.R.A.S 41AC-2 LEMO Outdoor Microphone with
RemoteCheck for Community & Airport Noise

www.gras.dk

LI0151 – 4 July 2017

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LI0151 – 4 July 2017

Revision History

Any feedback or questions about this document are welcome at [e-mail].

Revision Date Description

1 26 August 2014 First edition
2 19 February 2015 Section about maintenance added
3 4 July 2017 42AG substituted for the obsolete 42AB

Copyright Notice

© 2014, 2017 G.R.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 document may be trademarks or registered trademarks of
their respective companies and are hereby acknowledged.

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Contents

Introduction .................................................................................. 4

Delivered Items ............................................................................. 4

Installation .................................................................................. 6

System Integration ...................................................................... 12

Maintenance .............................................................................. 13

Accessories ................................................................................ 14

Specifications ............................................................................. 14

Calibration, Warranty and Service ................................................... 18

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Introduction

The G.R.A.S. 41AC-2 LEMO Outdoor Microphone with RemoteCheck for Community & Airport
Noise is a precision microphone set (IEC 61672-1) for monitoring community noise and the noise
of overhead aircraft.

It can be used for monitoring of noise with 90 degrees of incidence, typically community noise.
With the proper correction data, it can be used for 0 degrees of incidence, typically noise from
overhead aircraft. A USB flash drive with correction data is part of the delivery.

It is waterproof, rated at IP-55, and can operate unattended over a wide range of weather condi­tions 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 Items

1/2" Ext. Polarized Free-Field Microphone, High Sensitivity 40AF-S2

1/2’’ RemoteCheck Preamplifier with integrated connector 26AJ

O-ring for preamplifier OR2038

USB flash drive with correction data for 0° (resolution: 1/12 octave)

Wind Screen AM0378

Release Tube (for LEMO connector) GR1794

Top cone

-

Upper housing -

Lower housing -

1” pole mount adapter RA0286

Tripod Adapter GR1096

Tripod thread adapter SK0017

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41AC-2 is delivered pre-assembled except for the windscreen and thread adapter.

2-piece
1” pole mount

adapter RA0286

Lower housing

Windscreen
AM0378

Top cone

Preamplfier 26AJ
with RemoteCheck

Upper housing

½" microphone
40AF-S2

Release tube

Tripod and thread
adapter SK0017

O-ring OR2038

Fig. 1. The parts of 42AC-2.

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Installation

Mounting 41AC-2 on Tripod or Pole Mount Adapter

The 41AC-2 is designed for permanent installation and therefore comes with an adapter for
mounting on a 1” pole. See Fig. 2 and Fig. 3, 3. The 41AC-2’s housing is attached to the mount­ing 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.