I got different speed reading. MCE trace say 3,500 rpm In actual, the stroboscope say 3,550 rpm. I rely on stroboscope as it has been already checked and calibrated. Speed ripple monitored by MCE trace is +/- 10 rpm. This is no load running. So I have checked the electrical frequency by monitoring the motor current. MCE trace say 233 Hz In actual, the oscilloscope say 237 Hz. This is 8 pole motor. I have no idea why imotion IMC101T is not accurate. pls advise
The reading on the MCE trace is dependent on the current through the motor winding. As the motor keeps on running there might be a change in the winding resistance due to a rise in temperature (heating effect). This, in turn, might lead to a change in current through the winding causing slight changes in the measured speed. Thus, in this case, the reading of the stroboscope is different (more accurate) from the MCE trace.