Getting to Know The Four Most Common Types of Temperature Sensors

A temperature sensor is an instrument which measures certain physical qualities of a substance like expansion, resistance, and electromotive force, to determine its thermal quality and convey it as a number. There are many materials which change with temperature and can therefore be used as temperature sensors.In this blog, we will look at each of these temperature sensors and how they work.

Temperature sensors can be divided into two major types: contact and non-contact. Contact temperature sensors must maintain contact with the substance you are measuring so that a heat exchange can take place. This type of sensor mainly includes resistance type, thermocouple, and PN junction temperature sensors. Non-contact sensors do not need to be in direct contact with a substance, but rather they measure its qualities through the heat radiation or convection it creates.The four most common temperature Sensors used are thermocouples, thermistors, resistance temperature detectors (RTD), and IC sensors.

What is a Thermocouple?

A thermocouple is the most commonly used temperature sensor available. Thermocouple sensors have the advantage of having a wide temperature range, are adaptable to a variety of environments, and have no need for a power supply. They are also typically the least expensive of the four listed here. A thermocouple consists of two metal wires connected at one end. When one end of the wires is heated, the electric potential energy at one end of the circuit will be different than the other. This electric potential difference can then be used to calculate the temperature. Thermocouple sensors are the simplest and most versatile temperature sensor, but their sensitivity is low compared to others and can be easily affected by the surrounding environment. Therefore, they are not suitable for measuring small temperature changes which require highly accurate readings. In use, the thermocouple can measure any temperature except 0.

What is a Thermistor Sensor?

Thermistor sensors are non-contact sensors which measure the temperature of an object from the heat radiation around it. Thermistors are made of semiconductor materials which exert less resistance in increased temperatures. The thermistor is very small and responds quickly to temperature changes making it the most sensitive temperature sensor. However, its small size makes it sensitive to self-heating errors. The thermistor measures the absolute temperature on two lines, making it more accurate than a thermocouple but also more expensive and with a smaller measurable temperature range. As such, the thermistor is well suited for tasks that require fast and accurate readings but should be treated with caution as exposure to high heat may harm the device.

What is a Resistance Temperature Detector (RTD)?

RTDs are precision temperature sensors which are made of a high-purity conductive metal or alloy. Its resistance increases with rising temperature and decreases with lowering temperatures, similar to a thermistor. An RTD works by converting temperature changes into voltage changes. A current is continually passed through the temperature sensor of the RTD and responds linearly to temperature changes. RTD is currently the most accurate sensor, and it has a better linearity than the thermocouple and thermistor. However, RTD is a sensor with slow response speed and cannot be used to measure temperatures above 660.

What is an IC Sensor?

IC sensors rely on integrated circuits (ICs) or microchips which can take temperature measurements and output analog or digital signals. They have a limited temperature range and most are used to measure temperatures from -55 to +150. IC sensors can be classified as either having an analog output or digital output. Analog output sensors are single function (only measuring temperature). They are also low in price, have small sizes, and provide fast response speeds. Digital output sensors make use of microelectronics technology which can convey both temperature data and related temperature control quantities.

Conclusion

Each of these four sensors have advantages and disadvantages to suit a range of applications. When choosing which temperature sensor to use, consider temperature range, accuracy, response time, stability, linearity, and sensitivity. Temperature sensors are used in many electrical appliances from household appliances to industrial machinery. If you are in search of reliable electronics components, ASAP Supply Chain, owned and operated by ASAP Semiconductor, is a comprehensive marketplace of new and obsolete aircraft and electronic parts. Whether the parts you need are new, obsolete, or hard-to-find, our dedicated team will help you find them and can offer a competitive quote. Send an RFQ today and receive a customized quote from our team of experts!