FIELD: measurement technology. SUBSTANCE: device has laser 1, beam splitter 2 mounted in way of beam, unit of photodetectors 6 and 6, pulse shaper unit 9 for forming pulses corresponding to spaces between commutator bars of electric motor, revolution sensor 8 sending signal simultaneously with pulse from pulse shaper output to preset commutator bar selection unit 10 forming pulse which opens electronic switch unit 11; signal from these units are furnished to signal summation unit 12 forming the pulse at output whose amplitude is proportional to radial shift of preset bar relative to axis of rotation; device is also provided with output signal shaper unit 13; voltage at output of this unit is equal to amplitude of pulses arriving from summation unit 12; device is also provided with oscillograph and recorder for recording this signal. Optical axes of beams are so located that one of them is partially overlapped by commutator bars and second beam is overlapped by axis of rotor. EFFECT: enhanced efficiency. 1 dwg
