| 摘要 |
PURPOSE:To realize a high sensitivity automatic monitoring system by adding input signal data obtained through three-phase inspection, when an analog input circuit is inspected, and further cancelling the cancellation error. CONSTITUTION:Sampling data iA(m) at point (m) of phase A input and stored sampliug data iA(m-nX6) at a time point preceding by (n) times of half period from the time point (m) are fed to an adder/subtractor 32a thus obtaining a signal iCNA(m) through formula 1. In similar manner, signals iCNB(m), iCNC(m) are obtained through adders/subtractors 32b, 32c for phases B and C. These signals are stored in memory circuits 34a, 34b, 34c. An adder 35 takes out iCNA(m), iCNB(m-4), iCNC(m+4) from the stored values and adds them. Then an amplitude operating unit 17 calculates an amplitude based on the sum and makes a judgement that the accuracy is normal if the amplitude is within a range of predetermined value K1. |
