Sensor apparatus and monitoring method of control system using detected data from sensor apparatus

A method for monitoring a system including a sensor apparatus, a control apparatus, and a monitor apparatus, wherein

• the sensor apparatus transmits, in a single transmission frame, detected data, update check data including a value that differs from a previous value at each transmission, and error check data that allow detection of errors in the detected data and the update check data, via a serial signal to the control apparatus;
• the control apparatus controls an object to be controlled in accordance with the transmitted detected data, and transmits the detected data, the update check data, and the error check data via a serial signal to the monitor apparatus;
• the monitor apparatus determines presence or absence of an error in the currently-received update check data based on the currently-received update check data and previously-received update check data;
• the monitor apparatus monitors the system based on the presence or absence of error in the error check data and the presence or absence of the error in the update check data;
• and
• the sensor apparatus does not transmit the transmission frame to the monitor apparatus.