The 1/2” MK 255 measuring microphone cartridge is designed for acoustical measurements in research and development and also for industrial use. Some applications include audiometry, the measurement of building acoustics and noise levels. Frequency range 3,5 Hz to 20 kHz, free-field. Sound pressure levels up to 146 dB. The microphone cartridge has a fixed layer of back electrets to supply the polarization voltage.
It is designed and very carefully constructed to ensure excellent long-time stability of the electroacoustical parameters. All essential components including the diaphragm are made of steel and the diaphragm is bonded by a special galvanic process. The rear electrode, holder of the backelectret, is insulated from the cartridge housing by a quartz glass plate. The diaphragm is protected against mechanical damage by a protection grid. Convenient measurement of each cartridge’s frequency response curve by applying a well-defined electrostatic field (400volts/dc,30 volts/ac) can be realized by removing the protection grid and using a calibration grid. The microphone cartridges have been artificially aged. The equalization of the static air pressure between the inside and outside of the MK 255 cartridge is by means of a capillary tube rearvented into the preamplifier. This enables the use of the optional TA 202 dehumidifier.
The cartridge uses the international standard thread 60 UNS which ensures compatibility with a wide range of calibration equipment and measurement devices available from many manufacturers. MK 255 can be used with different measurement microphone preamplifiers as MV 204 (conventional LEMO connector), MV 210 (current powered version with BNC plug), with phantom powered preamplifier MV 220 as well as other preamplifiers without 200 V polarization voltage. The microphone cartridge can be calibrated and are designed for sound level meters of Type 1 according to DIN EN 60 651 and DIN IEC 61672. The TA 202 dehumidifier can be screwed between