To measure rotating speed with high accuracy without lowering of resolution even in a high speed rotating speed area by computing rotating speed on the basis of the difference between the count values of countes latched every sampling cycle.
A rotational pulse counter 3 counts signals from a rotational pulse generating means 2, and a time counter 5 counts clock pulses from a reference signal generating means 9. A prestorage means 6 latches the count value of the time counter 5 every input of the rotational pulse signals, and storage means 4, 7 respectively latch the count value of the counters 3, 5 every specified sampling cycle. A computing means 10 computes the rotating speed of a rotor every prescribed sampling cycle on the basis of the difference between the count value of the countes 3, 5 latched this time by the storage means 4, 7, and the previously latched count value of the counters 3, 5. A control means 8 supplies sampling signals to the storage means 4, 7 every prescribed sampling cycle.
SHIMAMURA KOICHI
YOKOYAMA KIYOAKI
