Signal amplifier MN 921

measuringmicrophonesingle-channel

The MN 921 is a one-channel measuring amplifier with a power supply unit for measurement microphones. Between the input and output a precision measuring amplifier with changeable amplification is connected. It adjusts the dynamic range of the measuring signal to the input dynamic of the following evaluation instrument. Additionally it is a driver for capacitive loading, e. g. long BNC-cables at signal outputs. The measuring amplifier is optional powered by batteries, accumulators or main. It provides all necessary voltages for a condenser measuring microphone (preamplifier-, polarization- and heater voltage). These voltages are absolutely indirect-coupled (no mains hum on the output signal) and are available on the LEMO-socket (MIC). The output for amplifier operating voltage (120 V) is short-circuit proof and the polarization voltage is controlled at ± 0,1 V. For pre-polarized measuring microphones the polarization voltage can be switched off. The MN 921 can supply measurement microphones with IEPE-connection in use with the adaptor A 92. The A 92 has a LEMO-socket and adapts on a BNC-connector. It exists a level indicator for visual control of output signal at BNC connector (OUT), which assures that the output signal is within the operating range of the amplifier. To dampen infrasonic disturbances on the signal you can switch a high pass second order before the output. When connecting the AC mains adaptor during operation in accumulator or battery modus, the MN 921 automatically switches to DC voltage from the mains adaptor. Thereby the charge of the elements in the battery box is reserved for the next use without mains adaptor.