GRAS 46AC 1/2'' LEMO Free-field Standard Microphone Set, Wide Frequency

Freq range: 3.15 Hz to 40 kHz
Dyn range: 20 dB(A) to 164 dB
Sensitivity: 12.5 mV/Pa
Use: For general acoustic diagnostics

Technology

Introduction

Through a close cooperation with our customers, we know that data-safety is highly important because the costs related to unsuited and unreliable sensors may determine whether your project turns into a success or not.

For our users, data safety translates directly into requests for easier microphone selection, simple system configuration and reduction of measurement errors.

To meet these requirements, we invented the microphone set concept. It is simple, reliable and robust and consists of a microphone cartridge and preamplifier combination, which is calibrated as one unit. This eliminates errors because there is only one sensitivity value to account for and the risk of contaminating the interface is eliminated. Combine this with our unique and proven design and you have the most reliable measurement microphone sets available in the industry today.

Typical applications and use

The 46AC is a free-field microphone set and as such optimized for all acoustic applications, where the location of the main sound source is known and the microphone can be pointed directly at it ensuring 0° incidence.

The high cut-off frequency makes it ideal for ultra-sonic diagnostics and impulse measurements, where minimum distortion and high resolution are obtained by the small size and fast response of the diaphragm.

Regarding temperature range, see the Specifications. Should higher temperature limits be required, we recommend considering  the GRAS probe microphones where the microphone and preamplifier can be isolated from the hot source.

Design

The GRAS 46AC is a high-performance 1/2” free-field standard microphone set for measuring medium sound pressure levels at high frequencies. In our clean-room environment the set is assembled and sealed with a label. However, the microphone set can be dismounted, if  you wish to use the components separately.

Microphone
The microphone cartridge is the high-quality IEC  61094 WSF2 standardized GRAS 40AC 1/2" Externally Polarized Free-Field Microphone, designed for long-term reliability in multiple environments.

Preamplifier
The preamplifier is the GRAS 26TK Preamplifier which is a special version inclusive TEDS of the GRAS 26AK 1/2" Standard Preamplifier with 7-pin LEMO connector, and based on our well-known circuit board substrates. In the industry these are famous for their low self-noise, wide frequency and excellent slew rate performance.

Compatibility

To perform as specified, the GRAS 46AC microphone set requires a power module or an analyzer input which can supply the preamplifier with power as well as 200 V polarization. If the power supply is lower, the capability of driving long cables is reduced and consequently the upper frequency is reduced. If the voltage supply is lower it will influence the upper dynamic range.

The microphone set is terminated with a 7-pin LEMO connector. Cables with LEMO connectors of various types and lengths are available in standard as well as customized lengths.

The 46AC is IEEE 1451.4 TEDS v. 1.0 compliant. If your measurement platform supports Transducer Electronic Data Sheets you will be able to read and write data like properties and calibration data.

System verification

The functionality of TEDS is very useful to determine which microphone is connected to which input channel. However, it is not a check of whether the microphone is within specifications or not. For daily verification and check of your measurement setup, we therefore recommend using a sound source like the GRAS 42AG Sound Calibrator.

For proper sensitivity calibration we recommend using a reference sound source like the GRAS 42AP Intelligent Pistonphone.

Calibration

When leaving the factory, all GRAS microphones have been calibrated in a controlled laboratory environment using traceable calibration equipment. Depending on the use, measurement environment and internal quality control programs we recommend that the microphone is recalibrated at least once a year.

We offer two kinds of calibration as an optional after-sales service: GRAS Traceable Calibration and GRAS Accredited Calibration.

GRAS Traceable Calibration is a traceable calibration performed by trained personnel under controlled conditions according to established procedures and standards. This is identical to the rigorous calibration that all GRAS microphones are subjected to as an integral part of our quality assurance.

GRAS Accredited Calibration is performed by the GRAS Accredited Calibration Laboratory that has been accredited in accordance with ISO 17025 by DANAK, the Danish Accreditation Fund.

If you want a new microphone set delivered with an accredited calibration in stead of the default factory calibration, specify this when ordering.

Learn more at gras/calib.

Quality and warranty

GRAS microphone sets are made of components from our proven standard portfolio and are all manufactured of high-quality material and branded parts that were chosen and processed to ensure life-long stability and robustness.

All parts are manufactured and assembled at the factory in Denmark by skilled and dedicated operators in a verified clean-room environment. The microphone diaphragm, body and unique protection grid are made of high-grade stainless steel and make the microphone set resistant to physical damage as well as corrosion caused by aggressive air or gasses.

This, together with the enforced gold-plated microphone terminal guarantees a highly reliable connection. Thanks to the high quality, our warranty against defective materials and workmanship is 5 years.

Service

Should you by mistake damage the diaphragm on a GRAS microphone we will in most cases be able to exchange it at a very reasonable cost and short turn-around time. This not only protects your investment but also meets your quality assurance department since you do not have to worry about new serial numbers etc.

Specifications

Frequency range (±1 dB)
Hz
5 to 16 k
Frequency range (±2 dB)
Hz
3.15 to 40 k
Dynamic range lower limit with GRAS preamplifier
dB(A)
20
Dynamic range upper limit with GRAS preamplifier @ +28 V / ±14 V power supply
dB
153
Dynamic range upper limit with GRAS preamplifier @ +120 V / ±60 V power supply
dB
164
Set sensitivity @ 250 Hz (±1 dB)
mV/Pa
12.5
Set sensitivity @ 250 Hz (±1 dB)
dB re 1V/Pa
-38
Output impedance
Ω
75
Power supply min. to max. (single/balanced)
V
28 to 120 / ± 14 to ± 60
DC-offset, min., single suppy
V
0.5 x Vs - 1
DC-offset, max., single suppy
V
0.5 x Vs + 4
DC-offset, balanced supply
V
-1 to 4
Microphone venting
Rear
IEC 61094-4 Compliance
WS2F
Temperature range, operation
°C / °F
-30 to 70 / -22 to 158
Temperature range, storage
°C / °F
-40 to 85 / -40 to 185
Temperature coefficient @250 Hz
dB/°C / dB/°F
-0.01 / -0.006
Static pressure coefficient @250 Hz
dB/kPa
-0.007
Humidity range non condensing
% RH
0 to 95
Influence of axial vibration @1 m/s²
dB re 20 µPa
62
TEDS UTID (IEEE 1451.4)
27 v. 1.0
Connector type
7-pin LEMO (FGG.1B.307)
CE/RoHS compliant/WEEE registered
Yes / Yes/Yes
Weight
g / oz
33 / 1.164
Specification Conditions

Typical frequency response. Upper curve shows free-field response for 0°, lower curve shows pressure response

Free-field corrections for different angles of incidence

GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.

Dimensions

Ordering info

Optional items

GRAS AA0008

3 m LEMO 7-pin - LEMO 7-pin Cable

GRAS AA0020-CL

Customized Length LEMO 7-pin - LEMO 7-pin Cable

GRAS AL0008

1/2" Microphone Holder, POM

GRAS AL0012

1/2" Microphone Holder, Stainless Steel

GRAS AL0005

Swivel head

GRAS AL0006

Tripod

GRAS RA0020

1/2" Nosecone

GRAS AM0069

Windscreen for 1/2" Microphones

GRAS RA0131

Rain-protection cap for 1/2” microphones

GRAS 12AA

2-Channel Power Module with gain, filters and SysCheck generator

GRAS 12AQ

2-Channel Universal Power Module with signal conditioning and PC interface

GRAS 42AG

Multifunction Sound Calibrator, Class 1

GRAS 42AP

Intelligent Pistonphone, Class 0

GRAS CA0029

Traceable Calibration of Microphone Set

GRAS CA2301

Accredited Calibration of Microphone Set

GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.

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