GRAS 40HF 1'' 低噪声传声器系统

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

GRAS 40HF 1 '' 低噪声传声器系统 40HF 可以测量远低于人类听觉阈值的声压级；即使是非常安静的产品，也非常适合用于声功率测量。其动态范围非常宽，可测量 20 Hz 至 10 kHz 范围内低于 - 10 dB re. 20 μPa（1/3 倍频程频带）的声压级。

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

Polarization/Connection

200 V / Traditional

Frequency range (±1 dB)

12.5 to 4k

Frequency range (±2 dB)

10 to 10k

Frequency range (±3 dB)

6 to 12,5k

Dynamic range lower limit (microphone thermal noise)

dB(A)

-2

Dynamic range upper limit

110

Set sensitivity @ 250 Hz (±2 dB)

mV/Pa

1100

Polarization voltage

200 V / Traditional

Microphone venting

Rear

Output impedance

Temperature range, operation

°C / °F

–20 to 60 / -4 to 140

Temperature range, storage

°C / °F

-40 to 85 / -40 to 185

CE/RoHS compliant/WEEE registered

Yes/Yes/Yes

Weight

g / oz

620 / 22

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 items

	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