23. 1'' Lownoise Microphone System- GRAS 40HF

Typical applications and use 典型应用和使用

-  Very Low Sound pressure measurements 
   极低的声压测量
-  Lownoise product measurements

   低噪音产品测量
-  Lowlevel Sound power measurements 

    低水平声功率测量
-   Measurements on hard-disk drives, computer products, quiet rooms etc.

     硬盘驱动器、计算机产品、安静房间等的测量

G.R.A.S.

More details

Freq range 频率范围 : 10 Hz to 10 kHz
Dyn range  动态范围 : -2 dB(A) to 110 dB
Sensitivity  灵敏度    : 1.1 V/Pa

GRAS

Design

The GRAS 40HF comprises:

  • a special high-sensitive 1-inch (23.77 mm) Condenser Microphone Type 40EH 特殊高灵敏度的1寸（23.77毫米）电容式麦克风40EH型
  • a special 1-inch (23.77 mm) Low-noise Preamplifier Type 26HF 特殊的1寸（23.77 mm）低噪声前置放大器26HF型

G.R.A.S

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).

前置放大器和麦克风是一个单独匹配的组合。 为了完成测量系统，需要一个特殊的电源模块，即GRAS 12HF用于单通道测量或GRAS 12HM用于多通道（1到10）测量。 所选的电源模块提供所有必要的电压，用于为前置放大器供电以及使麦克风极化。

G.R.A.S.

Microphone麦克风

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.

GRAS 40EH是一种外部极化麦克风，具有特别降低的固有本底噪声，以实现高动态范围和宽频率范围。 其隔膜经过特殊调整、可产生高灵敏度、同时产生低内部噪声。

G.R.A.S.

Frequency response and noise floor 频率响应和本底噪声

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 G.R.A.S. 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.

所选择的电源具有用于选择要使用的麦克风操作，即压力或自由场的两位置开关。当GRAS 40HF切换到自由场操作时，数据表中显示0°入射角的典型自由场响应。 数据手册中还显示了一个完整的低噪声测量系统，即线性和A加权情况下1/3倍频程帶的典型本底噪声。

G.R.A.S 

Measure beyond the threshold of human hearing

G.R.A.S.

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