| 摘要 |
PURPOSE:To improve the indication resolution in a high rotating speed range without increasing the counting capacity of a counting circuit by switching the counting period of reference pulses from one period counting to plural-period counting. CONSTITUTION:A period control circuit 3, a period switching control circuit 5, a decision circuit 7, a dividing circuit 8, a comparing circuit 9, etc., are provided. When a counted value N becomes less than a specific value, the circuit 5 lowers a period switching signal ef from H level to L level to switch the counting period of the circuit 3 from one period to two periods, thereby increasing the count number of reference pulses Pc1. At the same time, the constant value of the circuit 8 is switched to two-period counting. Consequently, the S (number of steps of pulse motor 14) outputted from the circuit 8 satisfies an integer sequence up to a higher number of revolution range of an engine. This S value is supplied to the circuit 9. The circuit 9 compares the counted value M of the counter 10 with '0' inputted from the circuit 7 or S value inputted from the circuit 8. Thus, the indication resolution in the high number of revolution range is improved.
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