SIGNAL DETECTION CIRCUIT AND HEATING DEVICE

PROBLEM TO BE SOLVED: To provide a signal detection circuit that can detect a signal input line being abnormally connected without increasing the number of components, is low cost, and meets the demand for size reduction.SOLUTION: In the signal detection circuit configured to input a detection signal of a thermistor TH to an A/D input port 11 of a microcomputer 1, a signal input line 2 to the A/D input port 11 is branched and connected to an input/output port 13 of the microcomputer 1. For diagnosis of a connection of the signal input line 2, the input/output port 13 is placed in an Hi-level output state, and it is determined from a current input value of the A/D input port 11 whether the signal input line 2 is abnormally connected. When the detection signal of the thermistor TH is read, the input/output port 13 is set as an input port.