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 46AM 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.
The microphone set can be used in temperatures up to 60 °C. Should higher temperatures be required, we recommend using the G.R.A.S. probe microphones where the microphone and preamplifier can be isolated from the hot source.
The G.R.A.S. 46AM is a high-performance 1/2” free-field standard microphone set for measuring medium sound pressure levels at a wide range of 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.
The microphone cartridge is the high-quality IEC 61094 WS3F standardized G.R.A.S. 40AM 1/2” Prepolarized Free-Field Microphone, designed for long-term reliability in multiple environments.
The prepolarization is obtained through an electret that is inflicted on the microphone back-plate under highly controlled conditions. The electret is then charged to match the specified microphone sensitivity.
The preamplifier is the G.R.A.S. 26CA 1/2” CCP Standard Preamplifier with BNC connector, and based on our wellknown circuit board substrates. In the industry these are famous for their low self-noise, wide frequency and excellent slew rate performance.
To perform as specified the G.R.A.S. 46AM microphone set requires a constant current input module that can deliver 4 mA and 24 V unloaded CCP voltage supply. If the constant current 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 BNC connector. Coax cables with BNC connectors of various types and lengths are available in standard as well as customized lengths.
The 46AM 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.
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 G.R.A.S. 42AB Sound Calibrator.
For proper sensitivity calibration we recommend using a reference sound source like the G.R.A.S. 42AP Intelligent Pistonphone.
Should you by mistake damage the diaphragm on a G.R.A.S. 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.
When leaving the factory, all G.R.A.S. 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.
Performance and warranty
G.R.A.S. 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 which guarantees a highly reliable connection, enables us to offer 5 years warranty against defective materials and workmanship.
|TYPE (Microphone features)||FF|
|Frequency range (±1 dB)||Hz||5 to 16|
|Frequency range (±2 dB)||Hz||3.15 to 31.5 k|
|Frequency range (±3 dB)||Hz||3.15 to 40k|
|Dynamic range lower limit with G.R.A.S. preamplifier||dB(A)||25|
|Dynamic range upper limit with G.R.A.S. CCP preamplifier||dB||149|
|Set sensitivity @ 250 Hz (±2 dB)||mV/Pa||14.5|
|Set sensitivity @ 250 Hz (±2 dB)||dB re 1V/Pa||- 37|
|Output Voltage Swing, min. @ 24-28 V CCP voltage supply||Vp||8|
|DC bias voltage, typ.||V||12|
|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||- 0.014|
|Humidity range non condensing||% RH||0 to 100|
|Humidity coefficient @250 Hz||dB/% RH||- 0.001|
|Influence of axial vibration @1 m/s²||dB re 20 µPa||66|
|TEDS UTID (IEEE 1451.4)||27 v. 1.0|
|CE/RoHS compliant/WEEE registered||Yes / Yes, Yes|
Typical frequency response. Upper curve shows free-fi eld response for 0°, lower curve shows pressure response.
Free-field corrections for different angles of incidence
Pistonphone, Class 1
Intelligent Pistonphone, Class 0
1-Channel CCP Power Module with A-weighting filter
2-Channel Universal Power Module with signal conditioning and PC interface
3 m BNC-to-BNC cable
10 m BNC-to-BNC cable
Customized length BNC - BNC Cable