Meaning and mechanism
The thermistor is a component that utilizes the change in resistance due to temperature variations. NTC and PTC thermistors exhibit different resistance changes when the temperature increases; their behaviors are distinct.
Placing an NTC thermistor in a voltage divider converts temperature changes to voltage changes. Calculate resistance from the measured voltage, then use a calibrated curve to convert resistance to temperature.
Relationships and conditions
β is the exponential R(T)=R₀exp[β(1/T−1/T₀)]. The temperatures T and T₀, which are included in the inverse, must be expressed as absolute temperatures K, not Celsius.
β is an approximate parameter within a limited temperature range. Actual measurements are influenced by sensor self-heating, thermal equilibrium delay, and errors in the reference resistor.
What to observe in the simulation
An NTC thermistor has lower resistance at higher temperature.
Self-heating, measurement noise and thermal lag are omitted. The calibration model assumes known β. Experiment on screen; do not reproduce this with real power supplies, outlets or high voltage.
Key relationships and symbols
R(T) = R₀ exp[β(1/T−1/T₀)]
| Symbol | Meaning | Unit |
|---|---|---|
| R₀, T₀ | Reference resistance and reference absolute temperature | Ω, K |
| β | Coefficient of the NTC temperature curve | K |
Worked example
Using the reference β, what temperature corresponds to a measured resistance of 10 kΩ?
25 °C
Common misconceptions
- If the Celsius temperature is directly input into 1/T, it does not result in an accurate temperature conversion.