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Resistance Temperature Detectors (RTD) and Thermocouple both are the most common types of sensor that are widely utilized for measuring temperatures. Both the sensors are usually given more importance since they are extremely easy to use. These generally help in avoiding the cumbersome methods of conversion, and yield results simply. The only point of difference RTD and Thermocouple have is their manufacturing variation and functional distinctions.
| Table of Content |
Keyterms: Resistance, Temperature, Thermocouple, Sensor, Conversion, RTD, Electrical uproar, Environment
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RTD
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An RTD (Resistance Temperature Detector) is a kind of sensor whose principle operation is to alter the resistance as per the change of temperature. In a nutshell, the resistance hikes as the temperature soars. Generally, the RTD is known to be a passive device.
The relationship normally held between the resistance and temperature is very familiar and is likely to be repeated over the course of time. It is incapable of generating an output completely on its own.
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RTD, or Resistance Temperature Detectors, are objects that include a kind of film which is prepared of wire coil, or oftentimes of pure metal. It is fit for the measurement of temperatures in several industrial components since they are particularly unsusceptible to electrical uproar. One of many instances of RTD are Textile production and Air Conditioning Applications.
There are several benefits of using RTD too. One of them is that it is extremely useful to measure a wide range of temperatures, even in extreme environments.
Uses of RTD
Here are some common uses of a RTD,
- Since it has a spectacular sensitivity rate over a broad spectrum, it is used for measuring temperature of earth elements, like air, liquid and even gaseous substances.
- It is used in household essentials, such as stoves, air conditioning applications, refrigeration applications, grills and more.
- It is used in textile production services as well.
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Thermocouple
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A thermocouple, like a RTD, is a kind of sensor that helps in measuring temperature. It typically has two dissimilar metal types adjoined together at one specific end.
Normally, at times when the junction of either metals are seen to be heated, there is a visible formation of voltage that has a customary relationship with the temperature. In general, thermocouples are utilized for a wide spectrum of applications, such as, in gas turbine exhausts.
It usually generates a temperature-dependent voltage as per the constant influence of the Seebeck effect. Further, the voltage is seen to be translated into a form of temperature.
Uses of Thermocouple
Here are some common uses of Thermocouple,
- Thermocouples are generally used in materials like thermometers, especially the ones used in hospitals and pharmacies.
- It is also utilized in thermostats as sensors to regulate, and read the temperature.
- It is also practically used in water heaters as well.
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Difference Between RTD and Thermocouple
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| RTD | Thermocouple |
|---|---|
| The range of measurement that a RTD follows is between -200°C to 500 °C | The range of measurement that a RTD follows is between −180 °C to 2,320 °C |
| It is intended for measuring lower temperatures. | It is intended for measuring higher temperatures |
| RTD is known to portray firm stability with low shifts | Thermocouples are known to portray a poor stability with the production of less repetitions over the course of time |
| RTD is generally famous for its accuracy. | Thermocouples usually exhibit inaccurate and substandard results. |
| RTD, due to its manufacturing benefits, are quite expensive than thermocouples. | Thermocouples, however, are usually very cheap, as opposed to a RTD |
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Things to Remember
- RTD, in simple words, is a type of sensor used widely for the measurement of temperature that is usually very low, such as -200°C.
- Thermocouples are another common sensor type that helps in measuring temperature, usually extremely high, such as when the temperature soars to 350°C in ovens.
- Unlike thermocouples, RTD exhibits a firm stability, which makes it suitable for measuring temperature with a tone of accuracy.
- Thermocouples are usually used in medical thermometers.
- RTD, however, usually comes handy in air conditioning appliances.
- RTD is a more famous choice than Thermocouple.
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Sample Questions
Ques. Explain RTD on a brief note. (2 marks)
Ans. A Resistance Temperature Detector (abbreviated to RTD or Resistance Thermometer) is a device that is used to measure the temperature by determining the resistance witnessed in a wire coil. It is a type of sensor used in a broad spectrum to measure temperature. More importantly, RTD is used to measure temperature that is usually very low, such as -200°C. The wire it uses is generally referred to as a temperature sensor. It gives a very stable accuracy in the measurements.
Ques. What is a Thermocouple? (2 marks)
Ans. A thermocouple, in simple words, is an electrical device that comprises two different conductors or points that helps in forming an electrical junction. A thermocouple, like a RTD, is a kind of sensor that helps in measuring temperature. Thermocouples, on a general spectrum, are utilized for a wide range of applications, such as in gas turbine exhausts and kilns. It is known to generate a temperature-dependent voltage due to the Seebeck effect it undergoes.
Ques. State three points of differences between RTD and Thermocouple. (3 marks)
Ans. Here are the points of differences between RTD and Thermocouple,
| RTD | Thermocouple |
|---|---|
| RTD is used to measure temperature that is usually very low, such as -200°C to 500°C | The range of measurement that a RTD follows is between −180 °C to 2,320 °C. |
| RTD is famous for producing accurate results. | Thermocouple usually generates poor and inaccurate results at times. |
| RTD is generally very expensive. | Thermocouple is comparatively cheaper. |
Ques. What are the uses of RTD? (3 marks)
Ans. The uses of RTD are briefly listed below,
- Since RTD is known to have a great amount of sensitivity rate over a broad spectrum, it is used for measuring temperature of earth elements, like air, liquid and even gaseous substances when required.
- RTD is also used in household essentials, such as stoves, air conditioning applications, refrigeration applications, grills, plastic processing and more.
- It is used in textile production services as well.
Ques. What are the general applications of Thermocouple? (5 marks)
Ans. Here are some general applications of Thermocouple,
- Thermocouples are generally used in materials like thermometers, especially the ones used in hospitals and pharmacies.
- Thermocouples are also utilized in thermostats as sensors to regulate, navigate and read temperature as well.
- Thermocouples are also seen to be practically used in water heaters as well.
- It helps in the diagnostics testing for diesel engines and machines alike.
- It is also used in several gas appliances, such as boilers.
Ques. Explain the basic point of operation of Thermocouples. (2 marks)
Ans. Thermocouple is usually seen to function as per the Peltier effect. What it means is that when we apply a voltage to work between the electrodes which are connected to the semiconductor, it then appears to generate the Peltier effect. Herein, the two electrical conductors are then seen to create two separate junctions in the temperature. Henceforth, the Peltier emf visibly conducts between the junction of the two individual circuits. The junction, in general, then generates a disparity in the temperature which effectively leads the thermocouples to work.
Ques. What are the benefits of RTD? (4 marks)
Ans. Here are some benefits of RTD to take into account,
- RTDs are best known to offer reliable and accurate measurements even at extreme environments, thus being one of the most critically appreciated temperature sensors put into daily usage.
- RTD has been famous for providing a great amount of sensitivity over narrow spans.
- RTDS are famous for offering long term stability.
- In general, RTD has been known to provide low susceptibility to EMI and RFI.
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