SLAVE UNIT, NODE UNIT, CONTROLLERS AND NETWORK SYSTEM

Providing a slave that can precisely measure operating time of an output device that is service information, without having effects on a control system. To Mix slave 13 connected to a field network 12, an actuator 14 and sensor 15 that detects completion of operation of the actuator are connected. Having a built-in timer, the Mix slave measures time from when OUT terminal to which the actuator is connected turns ON until IN terminal to which the sensor is connected turns ON, by using the timer. Time thus obtained will be operating time of the output device. Comparison of this operating time with a setting will determine whether or not the actuator normally operates.