If a system requires a single control loop or discrete devices then a single loop controller can be used to control a thermal or process machine. These instruments can range from the very basic - single, manual, setpoint changes, through to sophisticated profilers which have the capability to execute multiple setpoint changes over a specified period of time.
Single loop controllers are typically front-of-panel products. These controllers provide a clear display on the front of the controller. The machine operator or engineer (end user) can use this display to set up the controller in situ and make subsequent program changes.