主题：兄弟.两肋插刀的时刻到了----关于"仪器校验"

标准活塞发声器校准,频率为250Hz或1000Hz,声压级为94dB或124dB

校准话筒,主要是校准其基准灵敏度,前提是其频率特性已知且不会发生大的变化.因此,一般校准一个频率点的灵敏度就足够了.

精确的实验室话筒校准,需用标准消声室和互易校准方法,能校准整个频段.

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因为声压跟温度和大气压力有关,所以需要测量温度和压力,哪个表就是气压表: barometer

A barometer supplied with the pistonphone gives the ambient pressure correction in dB, in the range 650 to 1080 hPa, provided it is checked annually to maintain its accuracy.

SATISFIED STANDARDS:
IEC 942 (1988) Class 1L (Class 0L with suitable external barometer)
ANSI S1.40-1984
NOMINAL SOUND PRESSURE LEVEL:
124 dB re 20 mPa ±0.2 dB at reference conditions:
Ambient Pressure: 1013 hPa
Ambient Temp.: 20 °C (68 °F)
Ambient Humidity: 65%RH
Effective Load Volume: 1.333 cm3
FREQUENCY:
Nominal: 250Hz
Actual: 102.4 Hz (ISO 266) or 251.2Hz ±0.1%
SPECIFIED MICROPHONE TYPES:
Brüel& Kjær (and similar types) 1², 1/2², 1/4² and
1/8² microphones (see calibration chart for more
details)
INDIVIDUAL CALIBRATION ACCURACY:
At Reference Conditions: ±0.09 dB
At Ambient Reference Conditions:
±0.12 dB with specified microphone types
Within Range of Ambient Conditions:
With External Barometer:
±0.15 dB — IEC942 (1988) Class 0L
With Included Barometer:
±0.30 dB — IEC942 (1988) Class 1L
NOMINAL EFFECTIVE COUPLER VOLUME:
19.733 cm3 (at 250Hz) including Nominal Effective
Load Volume 1.333 cm3
TOTAL HARMONIC DISTORTION: <3%
AMBIENT CONDITIONS:
Ranges:
Pressure: 650 hPa to 1080 hPa
Temperature: –10 to +50 °C (14 to 122 °F)
Relative Humidity: 5% RH to 95%RH
Required Measurement Accuracy:
Pressure: ±0.3% (IEC 942 Class 0L)
±2.0% (IEC 942 Class 1L)
Temperature: ±5 °C
Relative Humidity: ±15% above 35 °C (95 °F)
(measurement is not necessary below 35 °C(95 °F))
Power Supply
Batteries: 6 ´1.5 V IEC Type LR6 (“AA” size)
Lifetime: Typically 40 hours with alkaline batteries
(continuous operation at 20 °C)
Check: Constant check via “250 Hz” light

G.R.A.S的话筒是什么型号?

Low-noise Measuring System comprising:
½-inch (12.7 mm) Microphone:. . . . . . . .Type 40AH
½-inch (12.7 mm) Preamplifier: . . . . . . .Type 26HH
(with 3 m cable and LEMO FGA.1B.307 plug)
Frequency response:
12.5 Hz - 10 kHz: . . . . . . . . . . . . . . . . . . . . . ±1.0 dB
10 Hz - 16 kHz: . . . . . . . . . . . . . . . . . . . . . . . ±2.0 dB
6 Hz - 20 kHz: . . . . . . . . . . . . . . . . .+2.0 dB, –3.0 dB
Nominal sensitivity:
System: . . . . . . . . . . . . . . . . . . . . . . . . . . 800m V/Pa
Microphone: . . . . . . . . . . . . . . . . . . . . . . . 80 mV/Pa
Microphone polarization voltage:
200 V
Dynamic range:
Upper limit: . . . . . . . . . . . . . . . . . 113 dB re. 20 μPa
Lower limit: . . . . . . . . . . . . . . . . 6.5 dBA re. 20 μPa

这种话筒似乎精度不够!

ACO7012话筒就不错,MLSSA推荐配套的:

 

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TYPE26XX是话筒前置放大器的型号,不是话筒型号

IEC711等效电路图如下:

 

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