There are basically three types of temperature controllers;

On-off controllers

It is a simple controller with only on and off options. The output to which the temperature is being controlled is either on or off. The device will only switch off the output when the temperatures being relayed go beyond the desired temperature, referred to as the set-point.

When heating something, for example food, the output, in this case a microwave is on when the temperature is below the set-point and on when the temperatures cross it. Since during the heating temperatures will go up and sometimes down as per the operator’s manipulations, the controller is designed to deal with these fluctuations.

This particular one has integral and proportional control. Due to these two additions, temperatures are controlled with stability and more accuracy. The intervention of the operator is minimal. This is the best temperature controller in the market. It is able to automatically adjust itself to those that on the output. PID is especially used in industries where the set-points change rapidly.

Proportional Controller

This controller is designed to counter the shortcomings of the on-off controller. Where the on-off controller requires to go on or off whenever the output nears the set-point, proportional controller reduces the temperature. This way, the output automatically cools down. The output also slows down as a result. The on-off proportioning is usually set at a ratio of 1:1 but could vary as the output approaches the set-point. When the temperature is almost at the set-point, the output goes off for a while to cool it down.

The science behind heating is interesting. When most of the time we are only interested in heating our food or water, it is amusing to read about all that happens behind the scenes.