Overcoming the control challenge
The simplest and cheapest form of controlling temperature is an on/off control. However, this control technique does have certain limitations, with the temperature overshooting and undershooting around the set temperature. This is exactly how we might have controlled temperature during our earlier experiment of heating water. However, the accuracy level is too low, and owing to overshoots and undershoots, there is a chance that the material being heated will be damaged, making it unusable. These fluctuations are unacceptable in many industrial applications. There are also applications where the heaters are assisted by coolers. Similar to the digital outputs connected to heaters, digital outputs are connected to coolers, and the controller takes the action of switching on heaters and coolers according to the need for temperature control.
The following diagram shows the typical functioning of an on/off control. We show the set temperature is 120°...