5 Minutes! Understand NTC Thermistors!
Release Date:
2021-11-15
Author:
NTC thermistor It is a simple temperature sensor that is very common in consumer electronics. An NTC thermistor is a typical semiconductor resistor with temperature sensitivity, whose resistance decreases gradually as the temperature rises. NTC thermistors are primarily manufactured from metal oxides such as manganese, cobalt, nickel, and copper using ceramic processing techniques. These metal oxide materials exhibit semiconductor properties, behaving in a manner strikingly similar to semiconductors like germanium and silicon under conductive conditions. At lower temperatures, these oxide materials have fewer charge carriers, resulting in lower resistance. As the temperature increases, the number of charge carriers grows, leading to a reduction in resistance.
NTC thermistor Depending on their application, NTC thermistors are classified into power‑type, compensation‑type, and temperature‑measurement‑type.
The temperature‑measurement range of NTC thermistors typically spans –10 to 300°C, though some models can handle even higher temperatures. Among their key parameters are the rated zero‑power resistance and accuracy—specifically, the resistance value at 25°C. When we refer to a thermistor’s resistance, we usually mean its value at 25°C. NTC thermistors are fabricated from polycrystalline ceramic materials doped with metal oxides, and different applications call for distinct materials and package types. When selecting an NTC thermistor, two critical parameters must be considered: the resistance at 25°C and the B‑constant (typically specified as 25/50°C). If these two values are identical, the thermistor’s resistance–temperature curve will closely match that of the replacement device, allowing for interchangeability.
The measurement of an NTC thermistor should be carried out in two steps: 1) Measure its nominal resistance at 25°C. For example, for a 100 kΩ NTC, use a multimeter or ohmmeter to measure the resistance at 25°C, record the reading, and compare it with the nominal value. 2) Measure its resistance at a specified temperature. For instance, place the 100 kΩ NTC in a thermostatic bath maintained at 60°C (it is recommended to use an oil bath, as the temperature in an oil bath remains relatively stable), record the measured value, and compare it with the nominal value.
NTC thermistors generally serve five primary functions: surge current suppression, temperature measurement, temperature compensation, liquid-level sensing, and over‑temperature protection.
By leveraging the self-heating characteristic of NTC thermistors, automatic gain control can be implemented, and they can serve as amplitude‑stabilizing circuits, delay circuits, and protection circuits in RC oscillators. They can also function as temperature‑sensing elements in applications such as induction cookers and electric heaters. NTC thermistors are suitable for temperature measurement, meeting the precision requirements of low‑temperature measurements. Typically, an NTC resistor is connected in series with a fixed‑value resistor; by measuring the voltage across the resistor pair, the NTC resistance can be determined, thereby providing an approximate value of the ambient temperature.
NTC thermistor With its excellent cost‑performance ratio, diverse package options, strong adaptability, and ease of use, it has become the preferred temperature‑sensing solution for engineers across numerous fields. It is widely employed in home appliances, the power industry, telecommunications, military science, aerospace, and many other sectors, boasting significant growth potential.
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