High sensitivity
Typical change in resistance is on the order of -3% to -6% per °C, giving stronger signal response than many other sensor types.
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About NTC Thermistors
NTC thermistors are among the most sensitive temperature sensing devices in general use for temperature measurement, control, indication, and compensation from -50 °C to +150 °C.
Defined by the R/T curve
The resistance / temperature characteristic is non-linear, predictable, and commonly specified by curve plus the resistance at 25 °C.
Flexible configurations
NTC thermistors are available as leadless chips, leaded devices, probe assemblies, and custom multi-sensor designs.
NTC thermistors are among the most sensitive temperature sensing devices in general use for temperature measurement, control, indication, and compensation across practical operating spans from -50 °C to +150 °C.
A thermistor is composed of a semiconducting material that behaves like a thermally sensitive resistor. Its primary function is to exhibit a change in resistance when its body temperature changes because of ambient temperature shifts or current-induced self-heating. By measuring the resistance of a thermistor in a non-self-heating mode, its temperature and the temperature of the surrounding medium can be determined accurately.
In some applications, thermistors are deliberately self-heated by an electrical current under controlled conditions. In that mode, a self-heated thermistor can be used to measure the flow of gases or liquids.
NTC Thermistor Basics
NTC thermistors, or negative temperature coefficient thermistors, decrease in electrical resistance as body temperature increases. PTC thermistors, or positive temperature coefficient thermistors, behave in the opposite way and increase in resistance as temperature rises.
North Star Sensors specializes in manufacturing precision NTC thermistors from basic raw materials through finished products, with each production step closely monitored and controlled.
The thermally sensitive material in an NTC thermistor is composed of tightly packed and sintered grains of metal oxides such as manganese oxide, nickel oxide, iron oxide, and copper oxide. These solid structures are semiconductive to electricity.
Electrical conduction in many manganese-based spinel NTC ceramics is commonly described by small-polaron hopping. Charge carriers are localized with small distortions of the crystal lattice and can move between mixed-valence ions such as Mn³⁺ and Mn⁴⁺ on equivalent octahedral sites. At higher temperature, thermally excited lattice vibrations increase carrier mobility, with the hopping rate following an Arrhenius-like dependence on inverse absolute temperature, exp(−Ea/kBT), so resistance falls. Note that an actual thermistor’s R/T behavior and long-term stability also depend on its composition, microstructure, thermal history, and operating conditions.
R/T Curve and R25
The resistance / temperature characteristic of an NTC thermistor is non-linear, predictable, repeatable, and can be reproduced to exacting specifications. Because this characteristic is non-linear, NTC thermistors are commonly defined by their R/T curve.
The resistance value of an NTC thermistor is typically referenced at 25 °C, abbreviated as R25. The most common R25 values used for NTC thermistor applications range from 100 ohms to 100,000 ohms, although values as low as 50 ohms and as high as 1 megohm can also be produced. Custom NTC thermistors can also be specified with resistance values point-matched at temperature points other than 25 °C.
Each thermistor composition, or mix, has a specific ratio of metal oxides that helps define the thermistor’s physical dimensions, its R/T curve characteristics, and its resistance at 25 °C. NTC thermistors typically exhibit a relatively large change in resistance versus temperature, on the order of -3% to -6% per °C, providing substantially greater sensitivity to temperature change than thermocouples and RTDs.
Available Configurations
NTC thermistors are widely used because they are available in a broad range of physical configurations, including leadless thermistors, leaded thermistors, and temperature probe assemblies.
- Leadless NTC thermistors may be soldered or epoxied to hybrid circuits.
- Leaded NTC thermistors may be mounted to a PC board or supplied with extension leads.
- NTC thermistor probes and assemblies protect the thermistor from the environment while placing it in an optimal sensing location. For fast-response applications, micro NTC thermistors can fit into a stainless steel 22-gauge needle.
Besides standard thermistor probe and assembly configurations, North Star Sensors can build custom NTC thermistor products to meet unique application requirements. When needed, other sensor technologies can also be incorporated into a probe design, including custom RTD and thermocouple assemblies.
Inside the lattice
Why an illustrative 10 kΩ NTC model changes by more than 4,000× from −50 °C to 150 °C.
Each glowing dot represents a charge localized with a small lattice distortion also called a polaron. At higher temperature, thermally excited lattice vibrations make barrier crossing more frequent. This illustrative model assumes a 0.34 eV activation energy. Drag the temperature and watch the Arrhenius factor change.
Schematic Mn³⁺/Mn⁴⁺ hopping network · equivalent octahedral sites (other cations omitted)
A schematic manganese oxide lattice. Glowing dots represent localized charges. Raising the temperature increases the illustrative hopping frequency between equivalent sites.
localized charge (schematic) local lattice distortion≈ illustrative vibration amplitude
Illustrative constant-B model (R₂₅ = 10 kΩ, B = 3950 K)
10.0 kΩ
Sensitivity α
−4.44 %/°C
Arrhenius factor
1 in 5.6×10⁵
Estimated rate / carrier
1.8×10⁷ s⁻¹
Hops on screen
0 /s
In the animation above, 43 Mn³⁺ sites carry localized charges and 65 Mn⁴⁺ sites can accept a hop.
The plunge · resistance vs temperature
One constant-B, 10 kΩ model from −50 °C to 150 °C. The vertical scale is logarithmic so each gridline is another 10×, and the curve still falls through nearly four of them, from 859 kΩ to 200 Ω. A Pt1000 RTD on the same axes barely moves. Drag the temperature and the marker rides the curve.
The activation term · Arrhenius factor exp(−E/kBT)
At fixed temperature, the Arrhenius factor exp(−E/kBT) is a straight line against energy on this log scale. Increasing temperature makes the line less steep. The marker shows the model's factor at the assumed 0.34 eV activation energy; it is a rate-model term, not a direct measurement of individual lattice kicks.
Model assumptions and limits: this is an idealized nearest-neighbor small-polaron schematic, not a simulation of a specific North Star Sensors composition. Resistance and sensitivity use the constant-B equation with R₂₅ = 10 kΩ and B = 3950 K. The corresponding Eₐ = kBB = 0.340 eV and an attempt frequency of 10¹³ s⁻¹ are modeling assumptions, not measurements of this schematic specimen. On-screen hops use a separate visual rate scale, about 6–8 orders slower across the displayed range. The idealized cycle retraces one curve, while real thermistors can exhibit hysteresis, aging, and resistance drift. Primary sources: Fritsch et al. (1998), Groen et al. (2001), Reimann & Töpfer (2021), and Li et al. (2022).