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The full form of RTD is Resistance Temperature Detectors and they are also known as Resistance Thermometers. It is a temperature sensor that operates on the measurement principle where the measurement changes with the temperature. It is a wire wrapped around in a glass and the wire is made of pure material like nickel, platinum, or copper. These thermometers are fragile and are mostly kept protected.
The thermocouple is an electrical device used for measuring temperature and comprises two dissimilar conductors which form an electrical junction. They are widely used as temperature sensors. These are interchangeable, inexpensive, and are supplied with standard connectors. These are self-powered and don’t require any external provocation.
It comprises two metals that are joined together to form junctions:
- Measuring or hot junction.
- Reference or cold junction.
Importance of Resistance Temperature Detectors
These thermometers are used to measure the temperature in industries and laboratories and they are widely known for their characteristics of stability, accuracy, and repeatability. They are made of platinum, are stable, and do not get affected by oxidation. They can measure similar temperatures very accurately, and have high repeatability.Benefits of Resistance Temperature Detectors
The benefits are mentioned below:- They give accurate measurements and are proven to be the most accurate temperature sensors
- Their range is from -200 C to 850 C
- They are very easy to reset
- They have excellent stability, sensitivity, and high repeatability
- Predictable and small long term drift
- They give firm outputs for a long period
- The connection wire is inexpensive and can be used for many years but can be shorter if used in regular higher temperatures
- They are immune to electrical noise
Applications of RTD
Resistance Temperature Detectors can be used in:- Stoves and grills
- Food processing
- Plastics processing
- Textile production
- Microelectronics
- Air conditioning
- Gas, liquid, and air temperature measurement
- Refrigeration servicing
Importance of the Thermocouple
The thermocouple is the most durable and easy-to-use temperature sensor. They give results fast, are used for a wide range of temperatures, and are user-friendly devices. They can be made using materials like iron, nickel and can also be made with expensive and rare materials like rhodium and platinum. They are small in size, give fast responses, are used for a wide range of products, oppose vibrations and shocks, and are easy to use. Uses of the Thermocouple They play an important role in engineering and science because of their fast response and smaller size. They can measure extreme temperatures accurately ranging from 270 to 2500 C. They are used in diagnostics testing, as hospital thermometers, and gas appliances such as ovens, heaters, and boilers. Application of the Thermocouples They are used in varied areas such as diesel engines, offices, businesses, homes, kilns, gas turbine exhaust, etc. Factors to choose the best temperature sensor- Temperature: RTD’s temperature is between -200 to 500 degrees Celsius and Thermocouples is from -180 to 2320 degrees Celsius, for the temperatures above 500 degrees Celsius Thermocouples are the only choice.
- Size: The diameters of Thermocouples can be lesser than 1.6 mm and of RTD is between 3175 to 6.35 mm.
- Accuracy and stability: RTDs have high accuracy and stability and thermocouples can be of a shorter time.
- Response Time: For fast response, thermocouples are the best choice than the RTD.
- Resistance Temperature Detectors are favourable for the measurement of low temperatures. Its measurement range is between -200 to 500 degrees Celsius whereas Thermocouples are for a larger range of temperatures. Its measurement range is between -180 to 2320 degrees Celsius.
- Resistance Temperature Detectors have better stability and high accuracy whereas Thermocouple has poor stability and accuracy.
- Resistance Temperature Detectors are highly sensitive so they register small temperature changes whereas Thermocouple’s stability is poor so the small temperature changes are not identified by it.
- Resistance Temperature Detectors response time is good but the Thermocouple has a very fast response time.
- Resistance Temperature Detectors output is linear whereas Thermocouples are non-linear.
- Resistance Temperature Detectors are expensive whereas Thermocouples are cheaper than them. With a similar style and temperature, the Resistance Temperature Detectors cost at least two or three more than the Thermocouple. Savings can be done as the installation of RTD is cheaper but that doesn’t compensate for the device’s high price.
- The mechanical robustness is good of the Resistance Temperature Detectors whereas of Thermocouples the robustness is very good.
- Resistance Temperature Detectors are connected with CU wires whereas Thermocouples are with extension-wire or thermo-wire.
