Typical applications and use
- Very Low Sound pressure measurements
- Lownoise product measurements
- Lowlevel Sound power measurements
- Measurements on hard-disk drives, computer products, quiet rooms etc.
The Type 40HF comprises:
- a special high-sensitive 1-inch (23.77 mm) Condenser Microphone Type 40EH
- a special 1-inch (23.77 mm) Low-noise Preamplifier Type 26HF
The preamplifier and microphone are an individually-matched combination. To complete the measuring system, a special power module is required and is available from G.R.A.S., i.e. G.R.A.S. 12HF for single-channel measurements or G.R.A.S. 12HM for multi-channel (1 to 10) measurements. The chosen power module provides all necessary voltages for powering the preamplifier(s) as well as polarizing the microphone(s).
The Microphone Type 40EH is an externally polarized microphone with a specially reduced inherent noise floor in order to achieve a high dynamic range and wide frequency range. Its diaphragm is specially tuned to yield high sensitivity coupled with low internal-noise generation.
The Preamplifier Type 26HF has a built-in overload indicator (which is repeated on the chosen power supply) and a frequency correction facility for both pressure-microphone operation as well as free-field microphone operation.
Dehumidifier RA0095 (optional)
For use when humidity is high and only with a rear-vented version of the G.R.A.S. 40EH Microphone. Order only at the time of ordering a Type 40HF.
Frequency response and noise floor
The chosen power supply has a two-position switch for selecting which microphone operation to use, i.e. pressure or free-field. A typical free-field response for an angle of incidence of 0 ° is shown in the data sheet when the Type 40HF is switched to free-field operation. Also shown in the data sheet is a complete low-noise measuring system, a typical noise floor in ⅓13-octave bands for both the linear and A-weighted cases.
|Frequency range (±1 dB)||Hz||12,5 to 4k|
|Frequency range (±2 dB)||Hz||10 to 10k|
|Frequency range (±3 dB)||Hz||6 to 12,5k|
|Dynamic range lower limit (microphone thermal noise)||dB(A)||-2|
|Dynamic range lower limit with G.R.A.S. preamplifier||dB(A)||TBD|
|Dynamic range upper limit||dB||110|
|Dynamic range upper limit with G.R.A.S. preamplifier @ +28 V / ±14 V power supply||dB||TBD|
|Dynamic range upper limit with G.R.A.S. preamplifier @ +120 V / ±60 V power supply||dB||TBD|
|Dynamic range upper limit with G.R.A.S. CCP preamplifier||dB||TBD|
|Open-circuit sensitivity @ 250 Hz (±2 dB)||mV/Pa||TBD|
|Open-circuit sensitivity @ 250 Hz (±2 dB)||dB re 1V/Pa||TBD|
|IEC 61094 designation||TBD|
|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||TBD / TBD|
|Static pressure coefficient @250 Hz||dB/kPa||TBD|
|Humidity range non condensing||% RH||TBD|
|Humidity coefficient @250 Hz||dB/% RH||TBD|
|Influence of magnetic field @80 A/m, 50 Hz||dB re 20 µPa||TBD|
|Influence of axial vibration @1 m/s²||dB re 20 µPa||TBD|
|CE/RoHS compliant/WEEE registered||No/TBD|
|Weight||g / oz||/ TBD|
|G.R.A.S. 12HF||Power Module (1 ch.)|
|G.R.A.S. 12HM||Power Module (10 ch.)|
|G.R.A.S. AM0363||Windscreens (set of 5)|
|G.R.A.S. RA0090||Pistonphone Coupler (for 94 dB re. 20 μPa)|
|G.R.A.S. RA0093||Tripod Adapter|
|G.R.A.S. RA0009||Dehumidifier (only relevant for 40HF)|
|G.R.A.S. AA0046||3 m Ext. cable|
|G.R.A.S. AA0047||10 m Ext. cable|
|G.R.A.S. AA0048||30 m Ext. cable|