| 摘要 |
PURPOSE:To materialize maintenance free by using the signal attained by operating the output of a filter, which has property equivalent to the transfer function of an analog filter, into a digital numeric value, receiving the signal obtained by converting the analogous quantity of electricity into digital not through an analog filter. CONSTITUTION:The signal on the quantity of electricity in a system is introduced from a transformer PT or a current transformer CT into an input converter 1. This input signal is input into a sample-and-hold circuit 3a through an analog filter 2, and is also input into a sample-and-hold circuit 3b not through an analog filter, and is converted into digital quantity with a multiplexer 4 and an A/D converter 5, respectively, and then, is stored in a RAM6. And, CPU 8 checks the accuracy of an analog circuit by detecting the relative error between the signal being operated from a signal, which is converted into digital not through a filter, into a digital numeric value after passing the filter having the property equivalent to the transfer function of the filter 2 and the signal being converted into digital through the filter 2. |
