| 摘要 |
PURPOSE:To make it possible to detect a phase difference stably by providing a feedback circuit which compensates an offset voltage and drift automatically. CONSTITUTION:Analog comparators 3 and 4 are applied with an AC voltage to be measured and a reference AC voltage respectively. The output of comparator 3 is led to phase difference counter 13 via exclusive-OR circuit 101 which provides exclusive-OR of the rising side of the reference voltage, and that of comparator 4 to phase counter 104 via exclusive-OR circuit 102 which provides exclusive-OR of the falling side of the reference voltage. The output of counter 13 is supplied to latch circuit 14 to find a difference between counters 13 and 104 and feedback to comparator 4 comes into effect so that the difference will be eliminated. Thus, feedback circuit 115 following OR circuit 102 is provided, and consequently the phase difference can be detected stably all the time by automatically compensating the offset voltage and drift. |
