Temperature Sensor is a very basic Sensor because temperature is the most common physical parameter in our world. Temperature measurement is required in many applications. So guys Have you ever think that “how can we measure temperature?” As you know that for measurement of any physical parameter we require sensors. These sensors convert physical parameter to electronic signal and after getting electronic data we can process and record parameter value.
For temperature measurement many type of sensors are available in market, and here in article I will cover some basic temperature sensors. So let’s begin
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What is a Temperature Sensor?
Temperature sensor is a device which can sense temperature and accordingly change its physical characteristic or electric parameter. It may be a RTD, TC Silicon device or IR Sensor etc. By changing its electrical parameter we get an electronic signal which is directly related to temperature.
Here Some Important Temperature Sensors are given below.
Thermometer is the most common type of temperature. You can easily find it in any clinic or in your class room lab. Well it works on expansion characteristic of Hg. It contain bulb of mercury and when it heated, mercury expands. Thermometer has a calibrated scale on thin glass tube. Here in this meter we can get temperature by mercury level on the scale. Here temperature can measure on Fahrenheit, Kelvin or Celsius. It is the simplest method but not accurate. It can use in non-critical application.
Resistance temperature detector or RTD
RTD is the most common and accurate sensor in nominal cost. A Resistance Temperature Detector is based on material resistance property which is directly affected by temperature. Every material has its own temperature coefficient (in case of Platinum it is very accurate) and due to this coefficient we can easily calculate temperature by measuring resistance value of a particular conductor. But RTD require some external power source for operation. Platinum RTDs are costly in nature but highly accurate but we can also use Nickle and Copper material for lower cost RTDs.
In RTD resistance measurement plays an important role that’s why in market 2 wires, 3 wires and 4 wires RTDs are available.
For measurement of -200 °C to 600 °C RTDs are the best option but for higher temperature Thermocouple is required.
Thermistors (Negative Temperature Coefficient device)
A negative temperature coefficient means, when temperature increases the resistances of negative temperature device decreases. NTC thermistors are very sensitive resistors. They can easily capture 0.05 °C and its response is also very fast. Its normal working range is -50 °C to 150 °C
Thermocouples are very well known temperature sensors. It works on Seebeck Effect. It consist two different metal wires, one junction these different wire is in high temperature zone (which we want to measure) and other end of these wires is connected for voltage measurement. As per Seebeck effect generated voltage is directly proportional to temperature at hot Junction Point. Each type of thermocouple has its own temperature and voltage characteristic which is easily available on internet.
Thermocouple has low accuracy but it can use for wide range of temperature. Its working range of temperature is -200 °C to 1750 °C but in industry for higher temperature (more than 300 °C) thermocouple is used. This is very rugged temperature element it comes in metal sheath. It is low cost sensor and can use for long distance.
Most popular type thermocouple is K type element. It is suitable for -200 °C to 1300 °C and it is used in many applications. Other types of thermocouples are J type, T type, R type S type etc. you can also refer given sheet for details.
Infrared Temperature Sensor
As you all know that every particle emits Infrared rays. Its wave length and intensity is directly depends on temperature of body. So infrared temperature sensor is nothing but a Infrared receiver or detector. By detection of IR wave we can easily calculate temperature of object. It is a non-contact type temperature sensor.
Semiconductor Temperature Sensor
A semiconductor temperature sensor is based on Integrated Circuits (ICs). These Sensors can be categorized in given type, based on its output.
- Current output temperature sensor
- Voltage output temperature sensor
- Resistance output silicon temperature sensor
- Diode temperature sensor
- Digital output temperature sensor
These temperature elements are less accurate and slowest in response but in range of 55 °C to 150 °C it offer high linearity and high accuracy. In market Temperature Sensor AD590 and LM35 are very popular component.
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