What is an NTC thermistor?
An NTC thermistor is a negative temperature coefficient thermistor , whose resistance decreases as the temperature increases and increases as the temperature decreases.
Because NTC thermistors are highly sensitive to temperature changes, they are widely used in temperature detection, temperature control, and temperature protection .
NTC thermistors typically consist of an NTC temperature sensing chip, leads, and a package structure. They can be manufactured in various forms, such as epoxy encapsulation, glass encapsulation, thin film structure, CP wire structure, and metal probe, depending on different application requirements.
Guangdong Xinshiheng has focused on the research and development and manufacturing of NTC thermistors and temperature sensors for more than 20 years. It can provide corresponding products and customized solutions according to customers' usage environment, temperature range and control requirements.
Working principle of NTC thermistor
The core characteristic of NTC thermistors is that their resistance decreases as temperature increases .
Within a certain temperature range, there is a relatively stable correlation between the resistance of an NTC thermistor and the temperature. When the measured temperature changes, the resistance of the NTC changes accordingly, and the control system can calculate or determine the current temperature by detecting the change in resistance.
The commonly used mathematical model for NTC thermistors is:
R = R₀ × exp[B × (1/T − 1/T₀)]
in:
- R : Resistance value at the current temperature
- R₀ : Nominal resistance value at reference temperature T₀
- B : B value, also known as material constant.
- T : Current absolute temperature, in Kelvin (K).
- T₀ : Reference temperature, in Kelvin (K).
In practical applications, NTC thermistors are usually used in conjunction with resistors, circuits, or control chips to convert temperature changes into electrical signals that can be recognized by electronic systems.
Main parameters of NTC thermistors
When selecting an NTC thermistor, one should not only focus on a single resistance value, but also consider multiple parameters comprehensively.
1. Nominal resistance
The nominal resistance value usually refers to the resistance value of an NTC thermistor at **25℃**. Common specifications include:
- 5KΩ
- 10KΩ
- 20KΩ
- 50KΩ
- 100KΩ
Different devices have different circuit designs, so it is necessary to select the appropriate nominal resistance value according to the control circuit and temperature detection range.
For example, a 10KΩ NTC thermistor is a common specification in temperature sensing applications.
2. B value
The B-value is one of the important parameters describing the temperature characteristics of NTC thermistors, reflecting the characteristic of resistance changing with temperature.
Common ways to represent B values include:
- B25/50
- B25/85
It should be noted that different B values correspond to different temperature-resistance curves. Even if two NTC thermistors have the same 10KΩ resistance at 25℃, their B values are different, and their resistance values may also differ significantly at other temperatures.
Therefore, in the NTC selection process, the resistance value and the B value usually need to be determined simultaneously .
3. Resistance accuracy
The resistance accuracy of NTC thermistors directly affects the temperature detection results.
Common accuracy grades include:
- ±1%
- ±2%
- ±3%
- ±5%
For general temperature detection applications, the appropriate accuracy can be selected based on actual needs; for high-precision temperature control equipment, it is necessary to further consider the resistance accuracy, B-value accuracy, and temperature curve consistency of the NTC.
4. Operating temperature range
NTC thermistors with different packaging structures and materials have different operating temperature ranges.
For example:
Their temperature resistance and applicable environments vary.
Therefore, when selecting a model, it is necessary to specify the minimum operating temperature, maximum operating temperature, and long-term operating temperature of the equipment .
5. Response time
Response time refers to the time required for an NTC thermistor to sense changes in ambient temperature and reach a specified temperature response ratio.
Generally speaking, the smaller the size of the temperature sensing element and the lower its heat capacity, the more efficient the heat transfer between it and the object being measured, and the faster the temperature response speed.
For applications that require rapid temperature feedback, such as 3D printers, coffee machines, heating devices, and battery management, response time is of particular concern.
What types of NTC thermistors are there?
Depending on the packaging method and structure, NTC thermistors can be designed in various forms.
Epoxy-encapsulated NTC thermistors
Encapsulated with epoxy resin, it features small size, reasonable cost, and flexible application, and is widely used in household appliances, electronic equipment, and temperature control products.
Glass-sealed NTC thermistor
The temperature sensing chip is sealed and protected with high-temperature glass, which has good high-temperature resistance and stability, and is suitable for high-temperature applications and applications with high reliability requirements.
Thin film thermistor
With its thin-film structure design, it features small size and fast response speed, making it suitable for batteries, precision electronic equipment, and space-constrained temperature detection scenarios.
CP line thermistor
It adopts a flexible CP wire structure, which features small wire diameter and flexible installation, making it suitable for confined spaces and complex wiring environments.
Metal probe temperature sensor
By combining NTC temperature sensing elements with metal probes, the probe size, material, and structure can be customized according to the installation method and usage environment, making it suitable for fields such as HVAC, home appliances, refrigeration, and industrial equipment.
Main application areas of NTC thermistors
NTC thermistors are characterized by their small size, high sensitivity, reasonable cost, and ease of integration, making them widely used.
New energy vehicles
It can be used for temperature detection in new energy vehicle thermal management, battery systems and electronic modules, providing temperature data for battery temperature management and system control.
Battery energy storage
It is used in energy storage batteries, battery packs and related electronic equipment to monitor the temperature of battery cells and key components.
HVAC
Widely used in HVAC equipment such as air conditioners, heat pumps, and fresh air systems, it is used to detect the temperature of indoor environments, pipelines, heat exchangers, and other locations.
Smart Home
NTC thermistors can be used for temperature detection in smart home and small appliances such as coffee machines, dishwashers, smart toilets, hand dryers, and fire detectors.
3D printers and copiers
Used for temperature detection of printheads, heating modules, and key internal components of equipment to achieve precise temperature control.
Grilling probe
By using a high-temperature resistant metal probe structure to detect the internal temperature of food or equipment, the real-time temperature measurement needs during the cooking process can be met.
Conclusion
Although NTC thermistors are small in size, they are important temperature sensing elements in many temperature control devices. The resistance, B value, accuracy, operating temperature, response time, and package structure all directly affect the final temperature measurement results.
Therefore, when selecting an NTC thermistor, a comprehensive selection should be made based on the actual application scenario, rather than simply choosing a product based on its resistance value.
If you already have the parameters, product drawings, or physical samples of NTC thermistors , you can provide them to the Xinshiheng engineering team, and we can evaluate and customize the product according to your application needs.
