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The application of temperature measurement is quite wide. Not only the production process needs temperature control, some electronic products also need to measure their own temperature. For example, computers need to monitor the temperature of the CPU, and motor controllers need know the temperature of the power drive IC. Now we will introduce the NTC thermistor temperature sensor.
Thermistors adopt semiconductor materials, most of which have a negative temperature coefficient, that is, their resistance decreases with increasing temperature.
Temperature changes can cause large resistance changes, so it is the most sensitive temperature sensor. However, the linearity of thermistors is very poor, and it has a lot to do with the production process.
Thermistors also have their own measuring tricks. With the advantage of small size, thermistors stabilize quickly and do not cause thermal load. But the thermistors are therefore very weak, and high current will cause self-heating. Since the thermistor is a resistive device, so any current source on it will cause heat due to power. Power is equal to the current squared times the resistance, so small current source should be used. If a thermistor is exposed to high heat, it will cause permanent damage to the thermistor.
The principle of the thermistor temperature sensor: Under a certain measured power, the resistance value of the NTC thermistor decreases rapidly as the temperature rises. Determine the corresponding temperature by measuring the resistance value of NTC thermistor, so as to achieve the purpose of temperature detection and control.
Negative temperature coefficient thermistors (NTC thermistors) are made of manganese, cobalt, nickel, copper and other metal oxides by ceramic process. These metal oxide materials have semiconductor properties and are completely similar to germanium, silicon and other semiconductor materials in conducting mode. At low temperatures, these oxide materials have a low number of carriers (electrons and holes), so the resistance is high; as the temperature increases, the number of carriers increases, and the resistance decreases. The resistance of NTC thermistors varies from 100 to 1,000,000 Ohms at room temperature, with a temperature coefficient of -2% to 6.5%.
Characteristics of thermistor temperature sensor:
1. High sensitivity and fast response;
2. High precision of resistance and B value, and good consistency interchangeability;
3. Adopting double layer sealing process, the thermistor temperature sensor has good insulation sealing, mechanical impact resistance, and bending resistance;
4. The structure is simple and flexible, which can be customized according to different design requirements of customers.
Applications of thermistor temperature sensor:
1. Microwave temperature sensor, air conditioning, refrigerators, freezers, water heaters, water dispensers, heaters, dishwashers, disinfection cabinets, washing machines, dryers, and other home appliances;
2. Automotive air conditioning, water temperature sensor, intake temperature sensor, engine;
3. Switching power supply, UPS uninterrupted power supply, frequency converter, electric boiler, etc.
4. Intelligent toilet, electric blanket, etc.