Main uses and precautions of NTC thermistors

In general, NTC thermistor refers to the Negative temperature coefficient thermistor, which is a sensor resistance that reduces the resistance value as the temperature rises. Metal oxides such as manganese, cobalt, nickel, and copper should be used as commonly used materials and made using ceramic processes. These metal oxide materials have semiconductor properties. After all, they are completely similar in conductive methods to semiconductor devices such as germanium and silicon. The following mainly introduces the application methods and uses of NTC thermistors in circuits.

When NTC is used for temperature measurement, monitoring, or compensation, it is usually necessary to connect a resistor. The selection of resistance value can be determined based on the key detection temperature area and the amount of current flowing through it. Generally speaking, resistors with the same temperature resistance value as NTC will be connected in series, and the current flowing should be small enough to prevent natural impact on detection accuracy. The detected signal is the partial voltage on the NTC resistor. If you want to obtain a more linear partial voltage and temperature curve, you can use the following circuit:

The Use of NTC Thermistors

According to the characteristics of the negative coefficient of NTC thermistors, NTC is widely used in the following scenarios:

Temperature compensation for transistors, mobile communication devices, ICs, and crystal oscillators

Temperature sensing of rechargeable batteries

Temperature compensation LCD

Temperature compensation and sensing of car audio equipment (CD, MD, tuner)

Temperature compensation for various power sources

Switching power supply and power circuit suppression of surge current

Specification for the use of NTC thermistors

1. Pay attention to the operating temperature of NTC thermistors.

Do not use NTC thermistors outside the operating temperature range, φ 5 φ 7 φ 9 φ The operating temperature of the 11 series is -40~150 ℃; φ 13 φ 15 φ The operating temperature of the 20 series is -40~200 ℃.

2. NTC thermistors should be used in maximum power environments.

The maximum power of each larger specification is: φ 5-0.7W φ 7-1.2W φ 9-1.9W φ 11-2.3W φ 13-3W φ 15-3.5W φ 20-4W.

3. Specification for use under high temperature and humidity conditions.

If it is necessary to use thermistors in high temperature and humidity environments, sheathed thermistors should be used. The closed part of the protective shell should be exposed to the environment (water, water), and the open part of the sheath should not come into contact with water and steam.

4. It cannot be used in hazardous substances and liquid environments.

Do not use it in Corrosive substance or in the environment in contact with electrolyte, salt water, acid, alkali and organic solution.

5. Protect the wires.

Do not excessively stretch and bend the wires, and do not apply excessive vibration, impact, and pressure.

6. Avoid burning electronic components.

Avoid installing electronic components that are easily heated around power type NTC thermistors. It is best to use products with higher wires at the upper end of the elbow and use NTC thermistors to raise them above other components on the circuit board to prevent heat from affecting the normal operation of other components.

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