In simple terms, overshoot is a temperature rise that exceeds the set-point defined by the temperature controller. This is generally caused by thermal oscillations characteristic of on/off control actions.
A basic temperature controller uses a simple on/off control to generate and maintain process temperatures through electrical heating. When switched on, the heater load continuously converts a voltage into heat which is monitored by an integrated thermocouple. This thermocouple feeds back the process temperature to the controller, which monitors actual process conditions against the user-defined setpoint. If the temperature rises above the setpoint, the voltage is switched off and the temperature subsequently drops. This process is conducted rapidly and synchronously, generally forming a tight waveform that oscillates around the user setpoint within an instrument-specific percentage of the controller’s full temperature scale.
Overshooting can be negligible if it occurs within an acceptable accuracy range. However, it can also contribute towards significant safety issues, particularly where temperature precision is critical to the process. In this blog post, Glas-Col explores how to minimize overshoot with temperature controllers.
Over Temperature Limiting Controls
A manual temperature controller allows users to regulate the output voltage to a heater load simply by adjusting the dial on the instrument. This is an imprecise technique that typically requires the use of additional thermometers to control process conditions with any degree of accuracy.
Ideal temperature control and monitoring will use a closed loop feedback system such as a PID controller to regulate heat oscillations associated with on/off operation. An error value is continuously calculated as a function of three critical parameters and fed back to the controller to ensure tight control of the proportional control band around the setpoint. This enables fully-autonomous regulation of overshoot conditions to maintain temperatures within a degree of the desired setpoint.
Where temperature overshoot poses a safety risk, PID controls may not be enough to maintain desired process conditions. Limit controls add an extra element of security for over temperature conditions, particularly for high-limit heating experiments. The OTP system from Glas-Col is designed to work in tandem with precision temperature controllers to provide outstanding overshoot control. It is a microprocessor-based digital indicator of safe process conditions with a simple indicator for safe or fail conditions. These user-friendly alarm indications may be essential for high-temperature heating processes in which overshoot could prove hazardous.
Temperature Controllers from Glas-Col
Glas-Col is one of the leading suppliers of laboratory instrumentation in the U.S. We offer an extensive range of manual and precision temperature controllers, with additional process limits to help maintain safe working conditions for essential heating processes.
If you would like to learn more about our temperature controllers, read our previous blog post: What is the Auto-Tuning Process on Temperature Controllers? Otherwise, do not hesitate to contact us directly.