| 摘要 |
PROBLEM TO BE SOLVED: To provide an analog input circuit monitoring device for highly accurately and continuously monitoring an analog input circuit. SOLUTION: The analog input circuit provided with an A/D converter 5 for converting the analog input signals of a prescribed frequency is provided with a test signal superimposing part 3 for continuously superimposing the analog test signals of a test frequency ft different from the N multiple (N is a natural number) of the prescribed frequency and superimposed signals by the superimposing part 3 are converted into digital superimposed signals by the A/D converter 5. Test signals are separated from the digital superimposed signals by a separation part 9, the test signals after separation are inputted to an input circuit abnormality judgement part 12 and the abnormality of the analog input circuit is continuously monitored. Preferably, the analog test signals are directly inputted to the A/D converter 5 as well and the abnormality of the input circuit is judged based on the comparison of digital conversion test signals by the A/D converter 5 of the directly inputted test signals and the test signals after the separation. |
