Introduction
The resistance-temperature (R/T) characteristic is one of the most important properties of an NTC thermistor.
Unlike a fixed resistor, an NTC thermistor has a resistance that decreases as temperature increases. Understanding this relationship is essential when selecting an NTC thermistor for temperature measurement and control.
1. What Is the NTC R/T Characteristic?
R/T stands for Resistance vs. Temperature. It describes how the resistance of an NTC thermistor changes at different temperatures.
For an NTC thermistor:
Temperature ↑ → Resistance ↓
At lower temperatures, the resistance is relatively high. As the temperature rises, resistance decreases rapidly.
Typical R/T characteristic: The curve above is an illustrative example based on a 10 kΩ NTC thermistor with B25/85 = 3950 K. Actual R/T characteristics vary according to the thermistor's resistance and B value.
2. Why Does Resistance Change with Temperature?
An NTC thermistor is made from semiconductor materials whose electrical conductivity changes with temperature.
When temperature increases, more charge carriers become available, causing electrical conductivity to increase and resistance to decrease.
This temperature-dependent resistance makes NTC thermistors useful for detecting and controlling temperature.
3. R25 and B Value
Two important parameters are commonly used to describe an NTC thermistor's R/T characteristic:
- R25 — Nominal resistance at 25°C, such as 10 kΩ.
- B Value — Describes the relationship between resistance and temperature.
A simplified Beta equation is:
where T is the absolute temperature in Kelvin.
A different B value produces a different R/T curve, even when two thermistors have the same R25 resistance.
4. Why Is the R/T Curve Important?
Understanding the R/T characteristic helps engineers:
- Select the appropriate NTC resistance and B value
- Match the sensor with the control circuit
- Determine the required temperature measurement range
- Improve temperature measurement accuracy
- Develop suitable temperature compensation and control algorithms
5. R/T Curve and NTC Selection
When selecting an NTC thermistor, R25 alone is not enough. The B value, temperature range, resistance tolerance and B-value tolerance should also be considered.
For example, two 10 kΩ NTC thermistors may have different B values and therefore produce different resistance values at the same temperature.
Conclusion
The R/T characteristic defines how an NTC thermistor responds to temperature changes. By understanding resistance, R25, B value and temperature range, engineers can select a suitable NTC thermistor for accurate and reliable temperature sensing.
Xinshiheng provides customized NTC thermistors with different resistance values, B values, tolerances, temperature ranges, sizes, encapsulation structures and wire configurations. If you already have a battery temperature sensor drawing or sample, Contact our engineering team to help select or develop a suitable NTC sensor solution.
