M 645

1/4inch, Free-field, 100kHz
M 645 is a 1/4-inch pre-polarized free-field measurement microphone, used for measuring the undistorted true sound pressure before the microphone is placed in the sound field.

Specifications

Parameter	Value
Dimensions	1/4inch
Sound Field Type	Free field
Polarization Voltage	0V（Pre-polarized）
Frequency Response	10Hz – 100kHz ± 3dB 20Hz – 50kHz ± 2dB
Dynamic Range	37dB（A）-154dB （1000 Hz 失真<3%）
Noise Floor	37dB（A）
Sensitivity	（5±1）mV/Pa (-46.0± 2) dB re 1V/Pa
Standard	IEC 61094-4 类型，WS3F
Typical Capacitance	＜7.0pF
Pressure Equalization Method	Post-equalization
Operating Temperature	-30℃ ~ 85℃
Temperature Coefficient	-0.012dB/℃
Humidity Coefficient	<0.1dB (0% - 90% no condensation )
Relative Humidity	0% - 90% no condensation
Static Pressure Coefficient	-0.01dB/kPa

Specifications

Types of Acoustic Fields	Free Field
Polarization voltages	0V（Prepolarized）
Frequency range	10Hz – 100kHz ± 3dB 20Hz – 50kHz ± 2dB
Dynamic range	37dB（A）-154dB（1000 Hz THD<3%）
Background noise	37dB（A）
Sensitivity mV/Pa(dBV/Pa)	（5±1）mV (-46.0dB) ± 2dB
Capacitance Typical	＜7.0pF
Operating temperature range	-30℃ to 85℃
Temperature coefficient	-0.012 dB
Storage conditions	Temperature：25℃±5℃，Humidity：50%±15%RH（Ensure the long-term stability of the sensor）
Humidity range non condensing	0 - 90% no condensation
Humidity coefficient	<0.1dB
Static pressure coefficient	-0.01dB/kPa
Net weight	1.7g
Gross weight	95g
Outer packaging dimensions	16cm10cm4.5cm(LWH)
Main Body	Stainless steel
Diaphragm	Nickel
Backplate	Stainless steel
Insulator	Quartz
Electret	PTFE (Teflon)