RTD vs Thermocouple
The resistance temperature detector (RTD) and thermocouple are two examples of devices used to monitor temperatures. Because their function is so similar, the two are often mistaken. Despite this, the RTD and thermocouple have distinct differences in their principle operation. An RTD uses a single piece of metal whose changes in resistance represent the changes in temperatures. On the other hand, a thermocouple uses two metallic wires which generate a difference in voltages at the junction which corresponds to the change in temperatures. This blog will explain both RTDs and thermocouples in depth, as well as their many differences.
As stated, the RTD is a temperature sensor that determines the temperature by measuring the resistance of the electrical wire. When the metallic wire is exposed to heat, there is a rise in resistance due to the variation in the heat of the wire. Subsequently, the resistance of the wire lowers when the heat decreases. In general, only metals whose resistance is well-known are used in RTDs so the change can be easily noted and recorded.
The most popular metals used in the construction of RTD include copper, nickel, platinum, and more. Platinum is used because it shows stable resistance temperature characteristics over a very broad operating range. Nickel is used because it remains linear up temperatures above 300 degrees centigrade.
Rather than using resistance to measure temperatures, thermocouples do so by using the voltage. A thermocouple is designed to generate the voltage due to the thermoelectric effect which states that temperature is voltage dependent. Thermocouples are composed of two different electrical wire conductors that combine to form an electric junction. The two wires are heated and the difference in their temperatures generates an electromagnetic field in the circuit. The circuit generates voltage which is measured at the junction, determining the temperature. Different metals are used in thermocouples to provide different temperature ranges and characteristics, but the most commonly used metals include copper-iron, copper-constantan and antimony-bismuth.
In addition to the aforementioned, there are five key differences between RTDs and thermocouples. They are:
- An RTD operates in the temperature range between -200 and 600 degrees celsius. A thermocouple offers a much wider range between -200 and 2,000 degrees celsius.
- In addition to a wider operating range, thermocouples offer a faster response time between 0.1 and 10 seconds as opposed to the RTD’s response time between 1 and 50 seconds.
- Thermocouples are more cost-effective than RTDs. Despite the initial cost being higher, maintenance cost is far lower.
- RTDs are generally considered more accurate than thermocouples.
- RTDs offer better stability than thermocouples due to the nature of its design. RTDs are specifically products to provide repeatable results over a long time period.
While thermocouples and RTDs each have distinct advantages and disadvantages, both are crucial tools in measuring temperature of equipment. Whichever one you need, you can find it at NSN Parts now.
At NSN Parts Now, owned and operated by ASAP Semiconductor, we can help you source all types of RTDs, thermocouples, electrical wires, and electrical conductors and deliver them with some of the industry’s best lead times. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at +1-780-851-3631 or email us at sales@nsnpartsnow.com. Our team of dedicated account managers is standing by and will reach out to you in 15 minutes or less.
