Accuracy and Stability of NTC Thermistors


Designing temperature probes for specific applications requires a series of choices that will help devices balance critical parameters that allow for application requirements. Selecting temperature sensors that meet specific goals is a crucial process. Two important performance characteristics that need to be considered are accuracy and stability.Thermistor, NTC Thermistors

In a good portion of electronic devices, accuracy refers to a devices ability to reflect actualities. When defining this ability in sensors, a user must prove traceability to an absolute. A thermistor absolute is defined by ITS-90. It uses transfer standards and a fixed-point cell. In the thermistor industry, temperature sensors are defined not more accurately than ±0.002˚C (between fixed points). It is unreasonable to assume that sensors can realize accuracy that is greater than the above value.

Commercial temperature sensors are not able to provide accuracy that is greater than ±0.002˚C. Thermistors are some of the most reliable and accurate sensors on the market.

Stability must be set for temperature for each specific application.Excessive shift, at operating temperatures, will ruin tight tolerances. A thermistor will shift resistance upward while it is running. The amount of shift is dependent upon construction methods. Thermistors are considered stable at and below room temperature, but as exposure temperature goes up, drifting will occur. Temperature cycling primarily affects stability through high-temperature cycles. A glass-coated bead thermistor can match and exceed stability. Bead-in-glass probes are very stable temperature sensors.

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