[P Action (Proportional Control Action)]
P action (or proportional control action) is used to output a manipulated variable (control output variable) that is proportional to the deviation in order to decrease the deviation between the process value and set point. A proportional band is set centering on the set point, and the output is determined with the following rules.
A manipulated variable that is proportional to the deviation is output when the process value is within the proportional band.
A 100% manipulated variable is output when the process value is lower than the proportional band.
A 0% manipulated variable is output when the process value is higher than the proportional band.
Smoother control than the ON/OFF control action is possible because the output is gradually changed near the set point according to deviation. However, if the temperature is controlled with the proportional action alone, it will stabilize at a temperature that is off from the set point (offset).
Note: If a Temperature Controller with a temperature range of 0°C to 400°C has a 5% proportional band, the width of the proportional band will be converted into a temperature range of 20°C. In this case, a full output is kept turned ON until the process value reaches 90°C, and the output is OFF periodically when the process value exceeds 90°C, provided the set point is 100°C. When the process value is 100°C, there will be no difference in time between the ON period and the OFF period (i.e. the output is turned ON and OFF 50% of the time.)
TEMPERATURE CONTROLLERS
As the name suggests, Temperature controllers are devices designed to regulate the temperature in various systems, such as industrial processes, heating and cooling systems, and laboratory equipment. This blog post will explore the basics of temperature controllers, their types, and their applications.
The Basics of Temperature Controllers
Temperature controllers operate by monitoring the temperature of a system and comparing it to a desired temperature setpoint. If the temperature is above or below the setpoint, the controller sends a signal to adjust the heating or cooling system to return the temperature to the desired setpoint. The controller continually adjusts the heating or cooling output to maintain the setpoint within a narrow temperature range.
Temperature controllers are used in various applications, including HVAC, refrigeration, ovens, and process control systems. They are designed to control precise temperature, minimize energy usage, and prevent temperature overshoot or undershooting.
Types of Temperature Controllers
The most widely used controllers are on-off controllers and PID controllers.
On-off controllers are the simplest type of temperature controller. They work by turning the heating or cooling system on or off when the temperature reaches a certain threshold. These are generally less accurate but low-cost.
PID (Proportional, Integral, Derivative) controllers are the advanced type of temperature controller. They use a combination of proportional, Integral, and Derivative control to provide highly precise temperature control. The Proportional control adjusts the output in proportion to the difference between the setpoint and the actual temperature, the Integral control corrects for any accumulated error over time, and the Derivative control anticipates the rate of change of temperature and provides early corrective actions.
Applications of Temperature Controllers
Temperature controllers are used in a wide range of applications, including:
Conclusion
Regardless of the type, temperature controllers are critical for ensuring the optimal performance and safety of the systems they control. PPI offers a broad spectrum of Temperature Controllers for General Purpose applications to more demanding process-specific applications. The variants cover different sizes, display systems (LED, LCD, Graphic LCD, and Color TFT), and advanced features (Built-in Timer, Data Recording, PC interface, Printer interface, and USB interface).