Mercy Electronics manufactures PID Temperature Controllers. Mercy Electronics offers water level controllers, fan speed controllers, starters, boiler controllers, etc. The PID Temperature Controllers is widely used in industrial control systems. The PID controller calculates an `error` value as the difference between a measured process variable and a desired set point. The controller attempts to minimize the error by adjusting the process control inputs. The PID parameters used in the calculation must be tuned to according to the nature of the system