How Is Temperature Stability Measured?

By Mary Johnson, Wavelength Electronics, Inc.

HOW STABLE IS A TEMPERATURE CONTROLLER?

Typically, a controller manufacturer will give temperature stability specifications over one hour and stability over 24 hours. There are several caveats to the testing that can only be exposed by understanding the test protocol as it compares to your application.

Our testing is standardized so you can compare specifications across units with your own configuration.

We use three specifications:

• Stability 1-hour, off-ambient
• Stability 24-hour, off-ambient
• Stability 1-hour, on-ambient

Stability is how close the actual load temperature stays to the setpoint temperature over time. We operate a temperature controller with a thermoelectric, laser diode, and thermistor. We monitor actual temperature of the sensor. Error is the difference between actual sensor and setpoint temperatures. Our typical (TYP) stability specification is three times the standard deviation of the error over the specified time period.