| 摘要 |
In a digital relay, the circuit for repetitively obtaining a digital measure of the amplitude I of an analogue current or voltage, I sincwt say, includes a self-checking feature to ensure that a correct measure of I is furnished despite errors in the sampling or computation processes. From the most-recent digitised samples of the input two or more separate computations of I are made (21, 22), either (i) using odd- numbered samples, say, for one computation and even-numbered samples for the other, or (ii) using the same samples for both but with different algorithms. The two computations are compared (3) and an output Y representing them supplied so long as they agree. If they disagree, the two present computations of I are compared (61, 62) with previous ones (4, 5) to identify which computation is wrong and furnish the correct one to the output Y. Three possible algorithms for the computations are disclosed. <IMAGE> |
