Digital Tachometer PMO 2150/ 2151, PMO 4150/4151

Digital tachometers are especially qualified for an exact measurement and monitoring of all time-related measurements, which can be converted into a proportional frequency by appropriate sensors. Rotational speed, velocity, flow rate and related measurements belong to these time-related measurements. Depending on the programming the device measures the absolute value, ratio, percental or absolute difference.


The generation of speed-proportional frequencies results from a pulse wheel mounted on the shaft, which is scanned by a remote sensor. For control technique applications high resolution rotary encoders are coupled directly to the motor shaft.

The measuring method is the multi period measurement principle and the frequency is determined by the reciprocal value of the measured periodic time. The number of periods considered at the measurement value is dependent on the adjusted measurement time and the level of the input fre- quency. If the period time of the input frequency is smaller than the adjusted measurement time, the frequency average is calculated on all periods, that were counted in the last measurement interval.

If the period time is longer than the adjusted measuring interval, the frequency is calculated from the last measured period.

The two-channel type PMO 2150/4150 records both channels simultaneously. For the calculation of a difference or ratio the measured values of both channels are taken over concurrently.



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