To directly display high-precision production cycle time by using the pulse signal not affected by the ambient temperature for the operating speed detection signal of a machine, measuring the revolving cycle of a rotary shaft with a digital timer circuit, and providing an indicator for a digital display.

The detection signal, which is generated when a revolving cycle measuring cam 3 fitted to a drive shaft 2 is rotated, is obtained by a sensor 4 as the pulse signal 6 set to an or off according to irregularities. When the drive shaft 2 is revolved (n) times per production cycle time and (m) irregularities are provided on the cam 3, the number of pulses per production cycle time becomes (m)×(n). A digital timer circuit 8 measures the time (cycle) per production cycle time based on the pulse signal 6 from the sensor 4 and the conversion factor of a conversion setting circuit 9. The production cycle time is sent to a digital indicator 10 an displayed as the digital signal.