| 摘要 |
The present invention can easily detect the presence or absence of disconnection in connection of an input signal line of a three-wire sensor which is connected to a sensor signal input device via a power source line, the input signal line, and a voltage reference line. The three-wire sensor includes: a detection means; a circuit switching means that reflects a change in the state detected by the detection means onto a change in the state of the input signal line; and a protection means that functions, when a predetermined voltage is applied thereto, as a bypass path for the circuit switching means. An inspection voltage which is higher than the rated voltage of the protection means and which does not damage the protection means is applied, the magnitude of a detected signal which changes in accordance with an inspection current flowing, during the application of the inspection voltage, through a path including the input signal line and the protection means is compared with a predetermined threshold, and thus, the presence or absence of disconnection in connection of the input signal line is determined. |
