Both instruments convert temperature readings into electrical signals. RTDs work on the principle of resistance, which happens uniformly with changes in temperature. Thermocouples operate on the principle that when two metals are joined together, there is a potential difference, at the point of contact, that varies with changes in temperature. Since both instruments are designed to measure a range of temperatures under varied conditions, it is difficult to decide which of the instruments is better than the other.
It is more useful to compare them by examining some of their specific qualities. The majority of temperature readings are taken in inhospitable environments where there is corrosive, oxidizing, and reducing atmospheric conditions.
In addition to the uncomfortable conditions, there are vibrations, noises, and electricity. RTDs are wire wound in protective casings and are rugged and immune to harsh and hazardous conditions. For added protection, RTDs can be coated with perfluoroalkovy PFA polytertrafluoroethlyene for use in plating baths and pressurized systems.
Thermocouples, with metal cases, are very capable of dealing with corrosive and oxidizing conditions. When exposed thermocouple junctions are used, care must be taken. A thermocouple costs far less than RTDs, which can cost two to three times more, capable of reading the same temperature range.
The difference in cost between thermocouples and RTDs is due to the lower production costs for producing thermocouples. RTDs and thermocouples respond quickly to variations in temperature with thermocouples being slightly faster. There are various adjustments that can be made to RTDs to enhance their response time.
There is little difference in the dimensions of the two instruments. They are small with a diameter of 0. Though it is doubtful, it may be necessary to check the mounting location to see which device will fit.
The construction and design of RTDs makes them susceptible to failure in environments where there are vibrations. Thermocouples are unaffected by vibrations and are capable of supplying readings in those conditions. RTDs require a power supply and voltage to operate. Thermocouples do not require a power supply and are unaffected by heat.
RTDs are far more stable and are capable of providing accurate and precise readings for a long time. Thermocouples produce electromagnetic fields EMFs that change over time because of oxidation, corrosion, and the changes in metallurgical properties of the sensing elements.
Once a thermocouple begins to drift, the effect is irreversible. For industrial uses, RTDs are far more accurate and can produce readings with an accuracy of 0. A thermocouple's accuracy is far less at 1C. The chart below offers a brief comparative tool for examining RTDs, thermocouples, and thermistors. Thermocouples are classified into types with each type being suitable for specific temperature conditions.
To accommodate the various environments, each class of thermocouple has a construction to match an specific application. Sensors are a necessary part of manufacturing used to measure physical phenomena using the properties of metals and fluids.
An essential measuring device is the resistance temperature detector, a precise, sturdy, and accurate piece of equipment that supplies data for application monitoring. The linear nature of RTD sensors, as well as their stability, has increased their use. Since the resistance of materials presents a predictable change, the use of RTD sensors provides consistent and accurate temperature measurements. RTD sensors are widely used in the automotive industry to measure engine temperature, air temperature, external temperature, and water levels.
In solar power applications, even distribution of heat is critical to the efficient and effective production of electricity. RTD sensors do not overheat and are ideal for use with heating applications.
They are placed in solar panels to monitor the temperature of the panels. This is also true of grid connected wind turbines as a means of measuring the fluctuation in temperature. The production of drugs requires close temperature monitoring and control. Increases and decreases in temperature can damage a batch and its formulation. Achieving the proper thermal capability is an essential part of research, formulation, testing, and production.
The unique nature of the pharmaceutical industry requires the construction of precise instruments designed to meet the requirements of diverse temperature readings. Much like the pharmaceutical industry, the chemical industry has strict requirements regarding temperature control. The results of research and experimentation necessitate maintaining an accurate and precise environment.
The various special chambers and integrated systems use RTD sensors as monitors and controls to ensure accuracy and safety. Recent developments have led to an increasing demand for high temperature control and thermal heating solutions for the semiconductor industry.
In the complex conditions of wafer processing, RTD sensors provide the necessary repeatability, accuracy, and stability. The industries listed above are only a few of the many applications that require the accuracy and precision of RTD sensors. Every aspect of food production requires constant monitoring of temperature. RTD sensors are used during manufacturing, storage, and shipping.
The use of RTD sensors for aerospace is somewhat like their application in the auto industry. In aerospace, they monitor the temperatures of engines, coolant, and compressors as well as fuel tanks and fire control equipment. All machinery and electric motors have to be monitored for increases in temperature, which could significantly damage production.
This is also true of windings, generators, ovens, and microwave power. Temperature control is crucial to patient care, especially in cases of infant incubators, respiration devices, and dialysis equipment. In sound production, amplifiers and transmitters use tremendous amounts of heat producing electricity that has to be controlled and monitored.
An endless number of consumer products use RTD sensors as a means of controlling temperature. Resistance temperature detectors have six major components, which are the resistant element, wire, tubing material, connection fitting, outer diameter, and termination.
The configuration of these components is what separates the various types of RTD sensors and their accuracy and capabilities. Though the capabilities of the various sensors are different, their basic components are the same.
A typical RTD has a resistant element made of platinum, nickel, or copper. These metals produce the most accurate and positive temperature coefficient. Platinum is the most common type of element because of its excellent corrosion resistance and long term stability. All metals produce resistance when there is a change in temperature. Elements for RTD sensors are specifically chosen for their linearity during temperature change. You must have JavaScript enabled in your browser to utilize the functionality of this website.
What is an RTD? A resistance temperature detector, also known as an RTD or resistance thermometer, is a type of temperature sensor. An RTD consists of a sensing element, wires to connect the sensing element to the measurement instrument and a support to position the sensing element in the process. RTDs are designed to ensure precise and repeatable temperature versus resistance characteristics.
The sensing element in an RTD is an electrical resistor that changes the resistance value as the temperature changes. The change in resistance with temperature happens at a predictable rate and can be measured to provide the temperature of a material of process. The sensing element in an RTD typically contains either a coil of wire or a substrate with an etched film of platinum.
The use of extension wires attached to the sending element allows the electrical resistance to be measured from a distance away from the process or material being measured.
To know more about the difference between RTD and thermocouple, take a look at this article. Many factors influence the properties of an RTD sensor.
Various materials, such as platinum, copper, or nickel, can affect the range and linearity. Element types can have effects too, like thin-film elements or wire-wound elements. We can also have sensors with two, three, or four wires. The most common version is three, but each option has its pros and cons. If you need help choosing the right temperature sensor for your application, take a look at our new temperature measurement smart assistant. To know more about RTD sensors, you can check this video below or can get in touch with our engineers!
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