In this guide
How NTC thermistors work
An NTC thermistor is a temperature-sensitive resistor whose resistance decreases as its temperature rises. A circuit converts the resistance change into a temperature reading or uses the change to control another function. The sensor element alone does not define system accuracy: the resistance–temperature (R/T) curve, measurement circuit, thermal contact, calibration and operating conditions all matter.
There is no single temperature range, tolerance or construction that applies to every NTC. TDK’s NTC application notes identify selection inputs such as temperature range, resistance range, accuracy, surrounding medium, response time and dimensions. Confirm these against the exact part data and installation.
Common NTC thermistor applications
Temperature measurement and control
NTC elements can measure temperature in appliances, HVAC equipment, refrigeration systems, electronics and battery assemblies. The right construction depends on where heat must be measured: a PCB-mounted chip, an insulated wire probe, a surface sensor and an immersed probe transfer heat differently. Specify the measured object or medium, attachment method, ambient conditions and required response—not just “NTC sensor.” For commercial refrigeration, see our refrigeration sensor selection guide.
For HVAC or building controls, match the complete resistance curve to the controller. A nominal 10 kΩ value alone does not establish that a Type 3 curve is compatible; see our 10K Type 3 NTC compatibility guide. Board-level designs may call for an SMD chip; compare package, R25/B values and assembly limits in our chip NTC selection guide.
Thermal protection and inrush-current limiting
Some NTC devices are selected to detect or control temperature, while power NTC inrush-current limiters use electrical self-heating as part of their operation. These are different design jobs. For an inrush limiter, evaluate cold resistance, rated current, energy, hot restart interval and the equipment’s startup conditions from the relevant datasheet. Do not select a sensing probe as a substitute for a power-rated limiter.
Temperature compensation
An NTC can compensate for temperature-dependent behavior in a circuit, but the chosen curve and circuit determine the resulting correction. Confirm the operating interval and component tolerances together, then validate the assembled circuit over that interval.
Benefits and design limits
NTCs provide a resistance change with temperature that can be read by a suitable circuit, and their small form factors can support compact assemblies. These characteristics are useful only when the chosen element and its mounting match the measurement job.
- Curve fit: R25 and a B value do not always describe the full operating range accurately. Use the manufacturer’s R/T table or validated curve for the intended interval. Our NTC equation guide explains the calculation limits.
- Self-heating: measurement current can warm the element and shift its reading. Check dissipation and circuit power, and verify error in the installed design. TDK discusses this in its digital NTC readout application note.
- Installed response: encapsulation, thermal contact, airflow, board copper and surrounding medium affect response. Validate the final assembly rather than assuming a bare-element value will transfer unchanged.
- Application qualification: suitability for regulated or safety-critical equipment must be established from the exact component, supplier documentation and end-product requirements; it cannot be inferred from the term “NTC.”
OEM selection checklist
To compare an NTC solution or request a quotation, provide:
- Function: temperature measurement, compensation, protection or inrush-current limiting.
- Required temperature interval, allowable system error and calibration approach.
- R25, tolerance, curve/B-value interval or requested R/T table, plus controller/circuit details.
- Sensor construction, dimensions, mounting method, medium and target response.
- Excitation or load conditions, self-heating limit, environmental exposure and qualification needs.
- Annual quantity, assembly constraints, inspection and traceability requirements.
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