What is an RTD (Resistance Temperature Detector)?

What_is_an_RTD_(Resistance_Temperature_Detector).pdf

Transcript:

[0m:4s] Hi I'm Josh Bloom, welcome to another video in the RSP Supply education series. If you find that these videos are helpful to you, it certainly helps us out if you could give us a big thumbs up and subscribe to our channel.
[0m:15s] In today's video, we are going to talk about a device that is used commonly in industrial applications for collecting temperature data.
[0m:23s] I am not talking about a thermistor or thermocouple, I am talking about a resistance temperature detector, or sometimes commonly referred to as an RTD.
[0m:34s] And RTD is a type of input signal commonly found in industrial monitoring situations. The same types of situations where you might find basic digital and analog signals coming into a PLC. Much like those digital and analog signals, depending on the PLC hardware that is being used, you can also input RTD signals into the PLC accurately to read temperature data in many different applications.

[1m:2s] In this video we will talk about what hardware makes up the RTD and how it works. We will also discuss some of the reasons RTDs are used instead of other temperature devices such as thermal couples or thermistor. At its core RTDs use a specific type of metal that depending on the resistance measured in that metal can determine the temperature. The actual measurement occurs at the element, which is a portion of the device that actually is able to collect the data needed to provide accurate temperature readings. There are many different types of RTDs, some more common than others. A few examples are first, the thin film element which uses a very thin layer of resistive metals adhered to a substrate, typically ceramic, then coated in glass or epoxy.
[1m:53s] Next is the wire wound element. This type of element can provide greater accuracy and wider temperature measurement ranges, however, can create stress on the element wire which can lead to slight measurement errors over time. Lastly is the coiled element quickly becoming the most common type of RTD element.

[2m:15s] The coil element combines ideas from the two previous types as well as additional design elements. This element allows for strain free measurement on the element wire while still providing very accurate measurements.
[2m:30s] So, how do these different RTD elements actually work?
[2m:34s] RTDs work off a very basic principle, which is the correlation between metal and temperature.
[2m:41s] As the temperature of the metal increases, the metal's resistance to allow flow of electricity increases. So it stands to reason that is the temperature of the RTD resistive element increases, the electrical resistance measured in ohms also increases.
[2m:59s] Understanding this resistance and its relationship with heat is what can give us an accurate temperature reading.
[3m:6s] Each metal has a certain resistance measurement at different temperatures. So based off the resistance that is measured in a given type of metal, we can determine what the temperature actually is. The most common types of metals used in RTDs are Platinum, nickel, or copper.

[3m:25s] So what are some of the advantages of using RTDs as opposed to other types of temperature measurement devices?
[3m:31s] First and foremost is the high level of accuracy they can provide.
[3m:36s] They also provide a very wide operating range which can make them a great option in many different applications.
[3m:43s] Also, because of their high accuracy level, they are often used in situations where temperature measurement is critical. A few disadvantages include the fact that RTDs are rarely used at temperatures above 660 degrees Celsius. Above this temperature, it can become difficult to prevent the metal from becoming contaminated by the metal sheet surrounding the RTD element. Also at lower temperatures, RTDs do not provide the same level of accuracy or resolution as thermistors, which is another type of temperature measurement device.

[4m:18s] As you can see for the most part, RTDs offer a great option for many different temperature measurement scenarios. Because of their reliability, high level of accuracy, and ability to measure a very wide range of temperatures, they are one of the most widely used temperature measurement devices today.
[4m:36s] For a full line of RTDs and thousands of other products, please go to our website. For more information or other educational videos, go to RSPSupply.com, the Internet's top source for industrial hardware. Also, don't forget: like and subscribe.