Using Wireless Measurements in Control Applications

Wireless transmitters may be preferred in applications where new measurements are required since the cost may be lower than that associated with installing wired transmitters. However, there is a significant differences in the frequency and manner in which a new measurement value is updated by a wired transmitter vs. a wireless transmitter. Such differences must be taken into account when a wireless measurement is used in closed-loop control. In this paper we examine how the PID has been modified to address control applications using wireless devices. The differences between this modified PID, known as the PIDPlus, and the traditional PID are discussed. Test and field test results are presented that show that the same quality control as wired PID can be provided by PIDPlus despite slower, non-periodic wireless measurement update and communication interruptions.