Thermistors tend to be more accurate than RTD's and suppliers of thermocouples, but they have a much more limited temperature range because of their marked non-linearity.
A Thermistor capitalizes on the fact that the electrical resistance of a material changes as its temperature changes. Thermistors rely on the resistance change in a ceramic semiconductor, with the resistance dropping non-linearly with a temperature rise.
Thermistors can be a low cost solution to temperature measuring. They tend to have large signal outputs and their small size permits fast response to temperature changes. UE Thermistors are used to measure temperatures from -45° to 260° C (-50° to 500° F)
Measurement Specialties offers high end manufacturer of temperature sensors through its recent acquisitions of BetaTHERM and YSI Temperature. Both companies specialize in negative temperature co-efficient (NTC) thermistors for precision temperature measurement in environments where there is a high cost of failure.
Thermistor-based temperature sensors exhibit a change in their electrical resistance in response to a change in ambient temperature conditions. They are highly-sensitive and have very reproducible resistance-versus-temperature properties. Thermistors can be further classified as either “Positive Temperature Co-efficient” (PTC thermistors) or “Negative Temperature Co-efficient” (NTC thermistors). Both PTC and NTC thermistors have distinct features and advantages that make them ideal for different end-use sensor applications. Whereas PTC thermistors demonstrate an increase in resistance when subjected to an increase in temperature, NTC thermistors demonstrate a decrease and are commonly used for more accurate temperature sensing. This accuracy makes them unique in their functionality in many applications compared to other temperature sensors/switches such as manufacturers of thermocouples or electromechanical industrial thermostats, which they are steadily replacing.
NTC thermistors are available in a wide variety of configurations and protective coatings to suit almost any application. The particular features and advantages of NTC thermistors compared to other sensor types include:
Large temperature sensitivity and broad range of function
Available in many physical forms and not constrained by material types
Interchangeable devices eliminate need for individual sensor calibrations
Good electrical noise immunity
Easy to interface to electronic instrumentation
Can be customized to optimize thermal response requirements
NTC thermistors are the most versatile and cost-effective temperature sensors in terms of satisfying typical selection criteria and in their inherent advantages over other sensor types.
