| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure the quantity of flow, by making difficult the occurrence of frequency variations of synchronous pulse signals with respect to the instantaneous variations of supply voltage. SOLUTION: A comparator in an AC synchronizing circuit 10 of generating pulse signals (synchronous pulse signals) synchronous with the frequency of a commercial power supply is a comparator 7', having a hysteresis function. A first threshold Vth1 and a second threshold Vth2, which is lower than the first threshold Vth1 are set at the comparator 7'. The comparator 7' compares the level of a voltage-divided AC signals from a voltage division circuit 6, with the first threshold Vth1, reverses the level of the synchronous pulse signals from an L level to an H level, when the level of the voltage-divided AC signals is greater than the first threshold value Vth1, and makes the level of the synchronous pulse signals inverted, from H level to L level when the level of the voltage-divided AC signals is less than the second threshold Vth2. COPYRIGHT: (C)2009,JPO&INPIT
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