STATE DETECTION APPARATUS

A state detection apparatus (1) includes a communication circuit (16) that transmits information to an external apparatus, a control circuit (12) that operates the communication circuit (16) at a first timing, a battery (11) that supplies electric power to the communication and control circuits (16, 12), and a first explosion-proof barrier (15) connected between a contact circuit (30) and the control circuit (12). The control circuit (12) applies a test signal, generated based on voltage from the battery (11), to the contact circuit (30) at a second timing arriving at shorter intervals than the first timing, acquires a detection signal indicating current flow in the contact circuit (30) due to test signal application, and regardless of the first timing, operates the communication circuit (16) when the detection signal is acquired to transmit to the external apparatus that the state of a device connected to the contact circuit (30) is abnormal.