What is PID? | Applications

Surely, the word PID appears many times during engineering exercises, lectures or work. In the following article, we have tried to describe in a few sentences what PID is.

PID is an internal algorithm stored in the memory of a control device. It can be treated as an additional function that improves control and regulation as it adapts to the system in which it operates.

Without automatic regulators, all regulation tasks would have to be done manually by people!

Example: Drying pipes after painting in a furnace.

In order to maintain a constant temperature in the drying process of pipes after painting, the operator would have to constantly look at the temperature indicator and control the gas valve supplying gas to the heater (Figure 1). If the temperature was too high, the operator would have to close the gas valve to raise the temperature to the desired value.

However, manual control of the process is tedious and tiring, so it has been automated a long time ago. To improve (automate) our drying process, we must:

- Install a temperature regulator with a built-in PID function,
- Use an electromagnetic valve that can be controlled by our regulator,
- Install a temperature sensor (e.g. PT 100) and connect the entire system.

To the PID controller, the desired temperature (Setting, SV - set value) to be maintained during the drying process must be entered. The actual temperature measured by the sensor is read directly from the controller (PV - process value) When everything is already running, the PID controller compares the actual temperature (PV) to the set value (SV) and calculates the difference between the two signals, also called the error (E).

Then, based on the difference between the set and actual values and based on the system parameters (temperature rise time, thermal inertia of the elements), the controller calculates the time at which the control valve for supplying gas is opened in order to maintain the set temperature! If the temperature rises above its set value (the controller will regulate), the device will make a correction and adapt.

In summary, the PID controller learns how to control the device in which it is installed.

Regulators often have a built-in Autotuning option, which allows for precise adjustment of the controller settings (P, I and D terms) for a specific system.

PID controllers are available in our online store:

https://termipol.pl/category/baza-strona-glowna-regulatory-temperatury?horizontal&filter=1