Applying Thermal Switches

By Mac Stuhler

Applying Thermal Switches

Thermal switch technology has been established in many industries for a number of years. In these high-tech times, there is still a place for electromechanical devices, since they are self-contained, reliable, and cost-effective. However, correlating precise production calibration with field conditions is not always a matter of applying a simple formula. The rate of temperature change varies per application and generally is not constant. Erratic flow rates, differences in heat transfer properties of media, and wide ranging ambient conditions are realities which favor a planned trial-and-error method.

Parameters required to specify a thermal switch are:

Thermal Parameters

  • Set point
  • Tolerance
  • Differential
  • Max/min head overshoot/undershoot
  • Repeatability

Electrical Parameters

  • Current
  • Voltage
  • Type of load
  • Endurance required, mechanical, electromechanical
  • *along with contact life, consider the effect on set point of heat generated by the load

Environmental Factors

  • Corrosives
  • Shock, vibration
  • Probe pressure

Mechanical Constraints

  • Terminations
  • Mounting (surface mount, probe, bulkhead)
  • Probe length

Mac Stuhler, Vice President of Control Products, Inc., has written an informative whitepaper detailing thermal switch parameters and how best to implement them.

IVT Thermal