Temperature measurement of NTC thermistor.infrared sensor module

　　Temperature measurement is one of the most common parameters for embedded system monitoring, and there are various temperature sensors available to achieve this goal. Sensor types can range from blackbody detectors to simpler and more common resistive sensors, as well as all sensors in between. In this article, I will briefly discuss the Negative temperature Coefficient (NTC) thermistor - the most commonly used temperature sensor in various embedded systems.

　　Thermistor

　　A resistor is a type of resistive element, usually made of polymers or semiconductors, where the resistance varies with temperature. Such devices should not be confused with resistance temperature detectors (RTDs). Typically, RTDs are more precise, expensive, and cover a wider temperature range.

　　There are two types of thermistors, characterized by how the resistance changes with temperature. If the resistance value decreases with the increase of temperature, we call this device Negative temperature coefficient (NTC) thermistor. If the resistance increases with temperature, the device is called a positive temperature coefficient (PTC) thermistor. Usually, PTC devices are used as protective devices, while NTC devices are used as thermal sensors. A very common application of NTC thermistors is to detect and control the PN junction of broadband laser diodes.

　　Another characteristic of thermistors is their cost. Low capacity typical thermistors are typically priced at $0.05 to $0.10 per chip. Low cost and easy-to-use interfaces typically make these devices highly attractive in embedded applications.

　　A typical thermistor detection range is -50 to+125 degrees Celsius. Most applications based on thermistors are used at temperatures ranging from -10 to 70 degrees Celsius, or within the typical commercial environment range as we know it.

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