The four major applications of thermistor sensor

　　The main component of the thermistor sensor is a thermistor. When there is thermal radiation around the thermal material, it will absorb the radiant heat, resulting in an increase in temperature and a change in the resistance of the material.

　　1. Thermistor sensor temperature measurement

　　As a thermistor sensor for measuring temperature, the structure is generally simpler and the price is lower. Thermistors without an outer protective layer can only be used in dry places; sealed thermistors are not afraid of moisture erosion and can be used in harsh environments. Due to the large resistance of the thermistor sensor, the resistance and contact resistance of its connecting wires can be ignored, so the thermistor sensor can be used in long-distance temperature measurement for several kilometers, and the measurement circuit mostly adopts bridge circuits. Using its principle, it can also be used as other temperature measurement and temperature control circuits.

　　2. Thermistor sensor is used for temperature compensation

　　Thermistor sensors can compensate for the humidity of certain components within a certain temperature range. For example, the moving coil in the head of a moving coil instrument is made of copper wire. As the temperature rises, the resistance increases, causing temperature errors. Therefore, the negative temperature coefficient thermistor can be connected in parallel with the manganese copper wire resistance in the loop of the moving coil, and then connected in series with the compensated component, thereby offsetting the error caused by the temperature change. In transistor circuits and logarithmic amplifiers, thermistors are also commonly used to form compensation circuits. Compensates for drift errors due to temperature.

　　3. Overheating protection of thermistor sensor

　　Overheating protection is divided into direct protection and indirect protection. For small current applications, the thermistor sensor can be directly connected to the load in series to prevent overheating damage to protect the device. For high current applications, it can be used to protect relays, transistor circuits, etc. In either case, the thermistor is closely combined with the protected device, so that there is sufficient heat exchange between the two, and once overheated, the thermistor plays a protective role. For example, an abrupt thermistor sensor is embedded in the stator winding of a motor and connected in series with a relay. When the motor is overloaded, the stator current increases, causing heat generation. When the temperature is greater than the sudden change point, the current in the circuit can suddenly change from a few tenths of a milliamp to tens of milliamps, so the relay operates to achieve overheating protection.

　　4. Thermistor sensor is used for liquid level measurement

　　When a certain heating current is applied to the NTC thermistor sensor, its surface temperature will be higher than the surrounding air temperature, and its resistance value will be smaller at this time. When the liquid is higher than its installation height, the liquid will take away its heat, causing its temperature to drop and its resistance to rise. By judging the change of its resistance value, you can know whether the liquid level is lower than the set value. The oil level alarm sensor in the car fuel tank is made using the above principles. Thermistors are also used in automobiles to measure oil temperature, cooling water mixture, etc.

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