{"id":2959,"date":"2026-06-05T14:38:23","date_gmt":"2026-06-05T06:38:23","guid":{"rendered":"http:\/\/www.imhotepluz.com\/blog\/?p=2959"},"modified":"2026-06-05T14:38:23","modified_gmt":"2026-06-05T06:38:23","slug":"are-resistance-temperature-detectors-linear-4836-f8d1f8","status":"publish","type":"post","link":"http:\/\/www.imhotepluz.com\/blog\/2026\/06\/05\/are-resistance-temperature-detectors-linear-4836-f8d1f8\/","title":{"rendered":"Are Resistance Temperature Detectors linear?"},"content":{"rendered":"

Hey there! I’m a supplier of Resistance Temperature Detectors (RTDs), and today I wanna chat about a question that often pops up: Are Resistance Temperature Detectors linear? Resistance Temperature Detector<\/a><\/p>\n

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First off, let’s get the basics down. An RTD is a temperature sensor that works based on the principle that the electrical resistance of a metal changes with temperature. The most common material used in RTDs is platinum, but you can also find ones made from nickel or copper.<\/p>\n

Now, the big question: linearity. In an ideal world, an RTD would have a perfectly linear relationship between resistance and temperature. That means if you plot the resistance on one axis and the temperature on the other, you’d get a straight line. But in reality, it’s a bit more complicated.<\/p>\n

Platinum RTDs, which are super popular in the industry, are pretty close to being linear over a certain temperature range. For example, in the range of -200\u00b0C to 850\u00b0C, a platinum RTD follows a well – defined curve that can be approximated as linear for many practical applications. The International Temperature Scale of 1990 (ITS – 90) provides a standard for the relationship between resistance and temperature for platinum RTDs.<\/p>\n

The resistance – temperature relationship for a platinum RTD is usually described by a polynomial equation. The Callendar – Van Dusen equation is commonly used to model this relationship. It’s something like (R_t=R_0(1 + At+Bt^2 + C(t – 100)t^3)), where (R_t) is the resistance at temperature (t), (R_0) is the resistance at 0\u00b0C, and (A), (B), and (C) are constants.<\/p>\n

For small temperature ranges, we can simplify this equation and assume a linear relationship. Let’s say you’re working in a temperature range from 0\u00b0C to 100\u00b0C. Over this short span, the change in resistance with temperature can be approximated as (\\Delta R = \\alpha R_0\\Delta T), where (\\alpha) is the temperature coefficient of resistance. For platinum, (\\alpha) is approximately 0.00385 \u03a9\/\u03a9\/\u00b0C.<\/p>\n

But as we move outside of these relatively small and well – behaved temperature ranges, the non – linearity becomes more apparent. At very low temperatures (below – 200\u00b0C) or very high temperatures (above 850\u00b0C), the resistance – temperature curve starts to deviate significantly from a straight line.<\/p>\n

So, why does this non – linearity matter? Well, if you’re using an RTD in a system where precise temperature measurements are crucial, you need to account for this non – linearity. For example, in a chemical process where a small temperature change can affect the reaction rate, an inaccurate temperature measurement due to non – linearity could lead to sub – optimal results or even safety issues.<\/p>\n

There are a few ways to deal with the non – linearity of RTDs. One common method is to use signal conditioning circuits. These circuits can take the non – linear output of the RTD and convert it into a linear signal. Another approach is to use software compensation. You can program a microcontroller or a data acquisition system to apply a correction factor based on the known non – linear relationship between resistance and temperature.<\/p>\n

As a supplier of RTDs, I’ve seen firsthand how different customers have different needs when it comes to linearity. Some customers are okay with a rough approximation of linearity for their applications. They might be using RTDs in less critical systems where a small error in temperature measurement is acceptable. For example, in a simple room temperature monitoring system, a small deviation from perfect linearity won’t make a huge difference.<\/p>\n

On the other hand, there are customers who require extremely accurate temperature measurements. These are often in industries like aerospace, pharmaceuticals, and semiconductor manufacturing. For these customers, we offer high – precision RTDs and provide detailed calibration data to help them account for the non – linearity.<\/p>\n

We also offer different types of RTDs to meet various needs. For instance, we have thin – film RTDs and wire – wound RTDs. Thin – film RTDs are more compact and have a faster response time, but they might have slightly more non – linearity compared to wire – wound RTDs. Wire – wound RTDs, on the other hand, are more accurate and have better long – term stability, but they’re a bit bulkier.<\/p>\n

When it comes to choosing an RTD, it’s important to consider your specific application. If you need high linearity over a wide temperature range, you might want to go for a wire – wound platinum RTD. But if size and response time are more important, a thin – film RTD could be a better choice.<\/p>\n

In conclusion, while RTDs are not perfectly linear, they can be made to work very well in a wide range of applications. With the right signal conditioning and calibration, you can get accurate temperature measurements even in the face of non – linearity.<\/p>\n

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If you’re in the market for Resistance Temperature Detectors and have questions about linearity or any other aspect of RTDs, don’t hesitate to reach out. We’re here to help you find the right solution for your specific needs. Whether you’re looking for a simple RTD for a basic application or a high – precision one for a critical system, we’ve got you covered. Let’s have a chat and see how we can work together to meet your temperature sensing requirements.<\/p>\n

Digital Temperature Controller<\/a> References:<\/p>\n