The RTD temperature sensor is based on the temperature dependence of the electric resistance of metals. As the temperature increases for metal, so does its electrical resistance. Of course, there\u2019s an intrinsic coefficient of resistance for all materials, and a positive value for this coefficient makes specific materials better than others for the measurement element role. With nickel and platinum, for example, there is near-perfect linearity that is introduced by their respective coefficients, resulting in high accuracy and precision across repeated measurements. Moreover, nickel and platinum are generally chemically stable and extremely resistant to corrosion. To ensure that the correlation between resistance and temperature is specified for all RTD manufacturers, there is even a standard (IEC 60751:2008; ASTM E1137) that determines the numerical relationship for platinum resistance elements.<\/p>\n\n\n\n RTD sensors are used anywhere where the time required for the measurement isn\u2019t a critical factor, but at the same time, accuracy is. This includes air conditioning units, refrigerators, stoves, lab ovens, and various types of micro-electronics, leveraging their electromagnetic immunity. Other areas of application involve air, gas, and liquid temperature measurement that is impossible with other types of thermometers. That said, plastic processing, petrochemical processing units, and textile production locations generally use RTDs extensively.<\/p>\n\n\n\n The thermocouple\u2019s working principle is based on the thermoelectric effect, which enables the measurement of temperature differences through the electric voltage differences and vice versa. As the name suggests, this sensor couples two thermoelectric materials of different conductivity, which results in the generation of voltage at a specified temperature range. <\/p>\n\n\n\n By knowing the correlation between temperature values and voltage values for specific metallic couples, we can build thermocouples that work on different temperature ranges and deduce the temperature and the measurement point. For example, some common metal pairs are two different nickel alloys, tungsten and rhenium alloys, gold and iron alloys, platinum and rhodium alloys, or platinum and molybdenum alloys. For this measurement method to work, the two wires need to start from a \u201ccold\u201d reference junction and get coupled on the \u201chot\u201d measurement point.<\/p>\n\n\n\n In general, we see thermocouples wherever the need for accuracy isn\u2019t that compelling. Moreover, and thanks to the fact that thermocouples can measure particularly high temperatures, we see them deployed in the steel industry. Gas appliance safety is also a field where thermocouples are extensively used thanks to their small size and robustness, and also because they are so quick to give a reliable measurement, allowing for short reaction times. Finally, we see thermocouples used in process and power plants, and close to arrangements that can produce vibrations.<\/p>\n\n\n\n <\/p>\n\n\n\n Of all the factors that you will have to consider before you make your choice, there are four fundamental factors that determine whether a particular thermometer type is suitable for the intended application or not. These are the temperature range, the size of the sensor, the accuracy of the measurements, and finally, the response time.<\/p>\n\n\n\n Having laid out all of the above factors, it is important to point out that each thermometer type offers a premium range of products that can decisively boost their operation potential while significantly smoothing out their disadvantages. <\/p>\n\n\n\n
<\/p>\n\n\n\n![\"Drawing](\"https:\/\/www.axcontrol.com\/blog\/wp-content\/uploads\/2020\/06\/Coil_Element_PRT.png\")
For this measurement method to work, the sensor needs to house the measurement element and deduce the temperature by measuring its resistance. The elements can constitute thin layers of platinum or nickel on a ceramic plate, metallic wire wound around an insulating core, coiled and strain-free elements, and various other types of specialized implementations.<\/p>\n\n\n\nPros of RTDs<\/h3>\n\n\n\n
Cons of RTDs<\/h3>\n\n\n\n
Common Applications of RTDs<\/h2>\n\n\n\n
Working Principle of Thermocouples<\/h2>\n\n\n\n
![\"Man](\"https:\/\/www.axcontrol.com\/blog\/wp-content\/uploads\/2020\/06\/3640384450_e111ee209c_b.jpg\")
![\"Thermocouple](\"https:\/\/www.axcontrol.com\/blog\/wp-content\/uploads\/2021\/03\/IS200VTCCH1C-1024x683.jpg\")
<\/a>Pros of Thermocouples<\/strong><\/h3>\n\n\n\n
Cons of Thermocouples<\/h3>\n\n\n\n
Common Applications of Thermocouples<\/h2>\n\n\n\n
Comparison Overview<\/strong><\/h2>\n\n\n\n
Property<\/strong><\/td> RTD<\/strong><\/td> Thermocouple<\/strong><\/td><\/tr> Temperature Range<\/td> -200 to 650 O<\/sup>C<\/td> 180 to 2400 O<\/sup>C<\/td><\/tr> Measurement Accuracy<\/td> 0.01 to 1 O<\/sup>C<\/td> 0.5 to 5 O<\/sup>C<\/td><\/tr> Reaction Times<\/td> 1 to 50 seconds<\/td> 0.1 to 10 seconds<\/td><\/tr> Diameter Size<\/td> 3 to 7mm<\/td> 0.5 to 2mm<\/td><\/tr> Long-Term Stability<\/td> Very Good<\/td> Depends<\/td><\/tr> Linearity<\/td> Yes<\/td> No<\/td><\/tr> Powering Requirements<\/td> Yes (10mA)<\/td> No<\/td><\/tr> Need for Calibration<\/td> Yes<\/td> Reference Junction<\/td><\/tr> Expected Lifespan<\/td> Good<\/td> Depends<\/td><\/tr> Electrical Noise Interference<\/td> No<\/td> Yes<\/td><\/tr> Ability to Withstand Vibrations<\/td> No<\/td> Yes<\/td><\/tr> Cost (generally)<\/td> Expensive<\/td> Inexpensive<\/td><\/tr><\/tbody><\/table> How to Pick the Right One For You<\/strong><\/h2>\n\n\n\n
Should You Go Premium?<\/strong><\/h2>\n\n\n\n