Motor speed in rev/min?

Question

I have the following question:

"A slotted disc is mounted on a motor shaft as part of a control system. The disc rotates through an optical interrupter device which produces a pulse stream output that is proportional to the motor shaft rotation speed. The disc has 120 equally spaced slots."

If the measured frequency of the pulse stream is 120 Hz, what is the motor speed in rev/min?

Answer 1

You measure 120 pulses per second (120 Hz) and there are 120 slots per rotation, so it is rotating at 1/sec or 60/minute

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