ALLPCB
Overview
NTC (negative temperature coefficient) thermistors are resistive sensors whose resistance decreases significantly as temperature rises. They are made from metal oxides such as manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), copper (Cu), and aluminum (Al) using ceramic manufacturing processes.
Resistance-temperature relationship
The resistance of an NTC thermistor approximately follows an exponential function of temperature and can be represented by a resistance-temperature characteristic curve. Because each resistance value corresponds to a specific temperature, measuring resistance provides a basis for inferring temperature.
Key characteristics for temperature measurement
- High sensitivity: the temperature coefficient is typically 10 to 100 times larger than that of metals, often in the range of -3% to -6%, allowing detection of temperature changes on the order of 0.1 °C.
- Wide operating range: common room-temperature devices cover approximately -55 °C to 350 °C.
- Small size: chip sizes can reach 0.3 x 0.3 x 0.2 mm or smaller, enabling measurements in gaps, cavities, or biological vessels where other sensors cannot fit.
- Flexible resistance selection: resistance values are available across a wide range, typically 0.1 to 1000 kΩ.
- Formability and manufacturability: they can be shaped into complex forms and produced in large quantities.
- Low cost relative to performance.
Applications
NTC thermistors are used as sensing elements for temperature, flow, and liquid level measurements; as control elements such as thermal switches and current limiters; and as circuit compensation components. They are widely used in household appliances, the power industry, communications, defense, and aerospace.
Common measurement methods
Temperature measurement with NTC thermistors is commonly implemented using bridge circuits or by interfacing the thermistor to a microcontroller for resistance-to-temperature conversion.
