What is thermal resistance?

Thermal resistance is a category of sensitive components. The resistance value of thermal resistance will change with the temperature. Unlike the general fixed resistance, it is a category of variable resistors and is widely used in various electronic components. Different from pure metals in the resistance thermometer, the materials used in thermal resistors are usually ceramics or polymers. The higher the temperature coefficient thermistor, the greater the resistance value when the temperature, the lower the thermistor of the negative temperature coefficient when the temperature is, the lower the resistance value, and they belong to the semiconductor device. The thermal resistance is usually a higher accuracy within a limited temperature range, usually -90 ° C? 130 ℃.

The main characteristics of thermal resistance

1. High sensitivity, its resistance temperature coefficient is more than 10 to 100 times larger than the metal, which can detect temperature changes at 10-6 ° C;

2. The working temperature range is wide, the normal temperature devices are applicable to -55 ℃ ～ 315 ℃, the applicable temperature of high temperature devices is higher than 315 ℃ (currently can reach 2000 ° C), and low temperature devices are suitable for -273 ° C to -55 ° C;

3. Small volume, can measure the temperature of the gaps, cavity and biological blood vessels that other thermometers cannot measure;

4. Easy to use, the resistance value can be selected arbitrarily between 0.1 ～ 100kΩ;

5. Easy processing into complex shapes can be produced in large quantities;

6. Good stability and strong overload capacity.

The principle of thermal resistance working principle

Thermal resistance is a sensor resistor, the resistance value of thermistor, which changes with the changes in temperature, which is different from the general fixed resistance. The resistance value of the metal increases with the increase of the planting, but the semiconductor is the opposite. Its resistance value has decreased sharply with the increase of temperature, and it presents non -linear.

When the temperature changes are the same, the resistance value of the thermistor resistance is about 10 times the lead thermal resistance. Therefore, it can be said that thermistor is particularly sensitive to changes in temperature. This temperature characteristics of semiconductor. It is because the conductive method of semiconductor is carrier (electronics, cave) conductive. Because the number of carriers in semiconductors is much less than free electrons in metals, its resistance is very large. As the temperature rises, the number of carrier flows participating in semiconductors will increase, so the semiconductor conductivity increases, and its resistivity will decrease.

Thermistor is a thermist component made of the characteristics of the semiconductor resistance with the temperature of the semiconductor. It is made of different metal oxides according to different formulas. Within a certain temperature range, according to the changes in thermal resistance value, the temperature changes of the measured medium can be known.

When installing the thermistor in the circuit, when the thermistor is the same as the ambient temperature, the action time is sharply shortened as the current increases; when the thermistor has a shorter action time and smaller when the ambient temperature is relatively high at the relatively high ambient temperature Maintain current and action current. When the circuit is working normally, the thermistor temperature is similar to the room temperature and the resistance is small, and the connecting the circuit will not hinder the passing of the current; when the circuit occurs due to the failure, the thermistor is increased due to the increase in thermal power. When the temperature exceeds the switch temperature, the resistance will increase in an instant, and the current in the circuit will quickly decrease to the safe value.

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