Patent ID: 8386862

Claim:
A fault diagnosis apparatus for a multi-channel analog input/output circuit, comprising: a signal source for generating and transmitting plural types of signals; a first switching circuit having at least two or more switches, said signals from said signal source being supplied to said switches; an analog-signal conversion unit to which said outputted signals from said signal source are supplied via said first switching circuit; and a diagnosis-voltage input unit into which test voltages are inputted, wherein said analog-signal conversion unit, further comprises: a multiplexer to which said outputted signals from said signal source are supplied via said first switching circuit, said multiplexer having channels whose number is equal to said number of said plural switches that said first switching circuit has; an analog/digital converter to which signals from said multiplexer are supplied; and an output processing circuit to which outputs from said analog/digital converter are supplied, said diagnosis-voltage input unit, further comprising: a test-voltage input circuit; a digital/analog converter to which said test voltages from said test-voltage input circuit are supplied; a demultiplexer to which analog signals from said digital/analog converter are supplied, said demultiplexer having plural output channels; and a second switching circuit having switches connected to said demultiplexer, number of said switches being equal to at least number of said output channels of said demultiplexer, and wherein, when said fault diagnosis is performed, analog test voltages from said demultiplexer are supplied as inputs into said respective channels of said multiplexer of said analog-signal conversion unit via said respective switches of said second switching circuit.