GRAS 40HF 1'' Lownoise Microphone System

Freq range: 10 Hz to 10 kHz
Dyn range: -2 dB(A) to 110 dB
Sensitivity: 1.1 V/Pa

Technology

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.

Design

The GRAS 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 GRAS, i.e. GRAS 12HF for single-channel measurements or GRAS 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).

Microphone

The GRAS 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.

Preamplifier

The GRAS 26HF Preamplifier 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 GRAS 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 GRAS 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 1/3-octave bands for both the linear and A-weighted cases.

Specifications

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 upper limit
dB
110
Set sensitivity @ 250 Hz (±2 dB)
mV/Pa
1100
Polarization voltage
V
200 V / Traditional
Microphone venting
Rear
Output impedance
Ω
47
Temperature range, operation
°C / °F
–20 to 60 / -4 to 140
Temperature range, storage
°C / °F
-40 to 85 / -40 to 185
Connector type
BNC
CE/RoHS compliant/WEEE registered
Yes/Yes/Yes
Weight
g / oz
620 / 22
Specification Conditions

Typical frequency response

Typical noise floor shown in ⅓-octave bands for both the linear and A-weighted cases

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

Ordering info

Included

 

High sensitive 1" microphone

 

Lownoise 1" preamplifier

Optional items

GRAS 12HF

1-Channel Power Module for Lownoise Systems

GRAS 12HM

10-Channel Power Module for Lownoise Systems

GRAS AM0363

Windscreen for 1" Microphones

GRAS 42AA

Pistonphone, Class 1

GRAS RA0090

Pistonphone Coupler

GRAS AL0006

Tripod

GRAS RA0093

Adjustable, high quality, stainless steel tripod adapter

GRAS RA0095

Dehumidifier for 1” microphones

GRAS AA0046

3 m LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system

GRAS AA0047

10 m LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system

GRAS AA0053-CL

Customized length LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system

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

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