FAULT DIAGNOSIS APPARATUS AND FAULT DIAGNOSIS METHOD OF MULTI-CHANNEL ANALOG INPUT/OUTPUT CIRCUIT

摘要

A fault diagnosis apparatus and method capable of simultaneously detecting the fault of a multiplexer and the fault of an A/D converter and isolating and identifying causes of these faults, the multiplexer and the A/D converter being used in a multi-channel analog input/output circuit. Test-voltage values are inputted from a diagnosis-voltage input unit into the multiplexer and the A/D converter constituting an analog-signal conversion unit, the multiplexer having plural channels, the A/D converter converting outputs from the multiplexer into digital signals, the test-voltage values being different from each other for each channel of the multiplexer. Comparisons are made between the digital voltage values and the test-voltage values inputted, the digital voltage values being outputted for each channel of the multiplexer. From this comparison result, it is judged whether the multiplexer is at fault or the A/D converter is at fault.