If you’ve ever stepped into a walk-in freezer at a grocery store at 2 a.m. or watched a lab technician monitor cryogenic sample storage for a pharmaceutical company, you’ve probably noticed how much temperature sensors take for granted—until they fail. As an RTD sensor supplier, I get questions every week: “Can your RTD sensors hold up in low-temperature environments?” The short answer is yes, but the long answer is way more nuanced than a simple “yes.” Over the 12 years I’ve spent working with resistance temperature detector (RTD) sensors, I’ve seen first-hand how choosing the wrong sensor for a cold environment can cost a manufacturer thousands in lost product, downtime, or even safety risks. Let’s break down what makes RTDs work in the cold, where they excel, where they struggle, and what to look for when picking one for low-temperature applications. RTD Sensor
First, let’s recap the basics of how RTDs function, because that’s key to understanding their low-temperature performance. RTDs rely on the principle that the electrical resistance of pure metals changes predictably with temperature. The most common RTD is the Pt100, made of 99.9% pure platinum, with a resistance of 100 ohms at 0°C. The relationship between resistance and temperature for platinum is defined by standard curves, most notably the ITS-90 (International Temperature Scale of 1990), which is the global standard for temperature measurement, especially in extreme conditions. Unlike thermocouples, which produce a voltage difference that can drift at low temps, RTDs measure resistance directly, which gives them far higher accuracy—critical when you’re working in environments where even a 0.5°C error can ruin a batch of material or put a patient at risk.
Now, the big question: How low can an RTD go? Most people assume RTDs only work down to -200°C or so, but with the right design, they can operate even lower—down to -270°C, just 3 Kelvin above absolute zero. That’s colder than the surface of Neptune’s moon Triton, by the way. But not all RTDs are created equal here. Platinum is the go-to metal for cryogenic and low-temperature applications because of its stable resistance curve and inertness. Other metals, like copper or nickel, have lower temperature ranges—copper RTDs typically max out at -180°C, and nickel RTDs can’t go below -60°C without losing accuracy or even becoming unstable. At my company, we stopped stocking nickel RTDs for low-temperature use about five years ago, because customers kept coming back with issues: readings that drifted by 2 or 3 degrees after just a few months in a -80°C freezer. Platinum’s structure doesn’t break down in cold temps like those other metals, so it’s the only reliable base metal for deep cold work.
But it’s not just the metal that matters. The sensor’s construction is just as important, especially when temperatures drop, materials get brittle, and condensation or ice can cause failures. For example, the wire that connects the platinum element to the lead wires is a common weak point in low temps. If you use copper lead wires for a sensor that’s going to sit at -200°C, the mismatch in thermal expansion between platinum and copper will cause stress on the joints over time, leading to broken connections or resistance changes. That’s why we spec all our low-temperature RTDs with lead wires made of the same platinum alloy as the element, or at least a matching metal like silver-plated copper with a thermal expansion coefficient close to platinum. We also use glass or ceramic insulators instead of plastic for internal parts, because plastic gets brittle at low temps and cracks, leaving the element exposed to moisture that causes shorts. I learned this the hard way early in my career: a customer bought a batch of cheap RTDs from a competitor for their cryogenic bioresearch lab, and within six months, 30% had failed because the plastic insulation on the lead wires cracked at -150°C. That’s when I started testing every single RTD we make in our environmental chamber, cycling them between room temp and -200°C for 100+ cycles, before we ship them. No cutting corners here.
Now, let’s talk about where RTDs shine in low-temperature environments, because that’s where most of our business comes from. First, cryogenic storage: think pharmaceutical companies storing vaccines, blood products, or cell lines at -80°C or lower. Vaccine makers especially need super accurate temperature monitoring—one bad batch of mRNA vaccine can cost millions, not to mention set back public health. RTDs are perfect here because they can measure down to -270°C with accuracy as high as ±0.1°C, way more precise than thermocouples (which usually have an error of ±1°C or more at low temps) or thermistors (which drift badly below -50°C). We supply RTDs to three major vaccine manufacturers in the U.S., and their labs tell us our sensors are the only ones that don’t drift over months of continuous use in their freezers.
Another big application is industrial freezing and food processing. For example, large food producers blast-freeze packages of meat or produce to preserve freshness, typically at -40°C to -60°C. If the temperature in the blast freezer is off by even a couple degrees, the food can’t be stored as long, or worse, it could develop ice crystals that ruin texture. RTDs hold up here because they’re not affected by moisture or frost the way other sensors are—wait, actually, let me correct that: frost can be an issue, but it’s not a sensor failure if the sensor is coated properly. We coat all our low-temperature RTDs with a dense epoxy or Teflon (for temps below -100°C, Teflon is better) that repels moisture, so frost doesn’t build up on the element and skew readings. I’ve seen thermocouples in blast freezers that got covered in frost and read 10°C higher than actual temp, but our RTDs stay accurate because of that coating.
Then there’s aerospace and research. If you’re testing a satellite component that has to survive the cold of outer space (which can be as low as -270°C for deep space), or a physics lab studying supercooled materials, RTDs are the standard. The European Space Agency even uses Pt100 RTDs for temperature monitoring on their Mars rovers, because they can handle extreme cold and deliver consistent data. We work with a number of university physics departments that run experiments on superconductors, which only work at temps below -135°C (that’s 10 Kelvin). Their sensors have to be accurate and stable for weeks on end, and RTDs are the only thing that meets their needs.
But RTDs aren’t perfect in low temps, and it’s important to know their limits, because misapplying them is the most common mistake we see customers make. First, power dissipation. RTDs work by passing a small current through the element to measure resistance, but if that current is too high, it will generate heat in the element itself, which can throw off readings, especially at low temps where the surrounding environment is already cold. For low-temperature RTDs, we spec a maximum excitation current of 0.1 mA, compared to 1 mA for standard room-temperature RTDs. If you use a 1 mA current, the element will get warm, and at -200°C, even a 0.1°C self-heating error is a big deal. I had a customer last year who was using an off-the-shelf RTD for their cryogenic lab, and they were running 1 mA through it. They were complaining their readings were 2°C lower than the actual temp, and we figured out it was self-heating. Swapping to our low-current RTDs fixed the problem immediately.
Another limitation: RTDs are slower to react to temperature changes in very cold environments, compared to thermocouples. That’s because the platinum element in an RTD is a small, coiled wire, and it takes a tiny bit of time for it to reach thermal equilibrium with its surroundings. If you need real-time temperature monitoring for a process that changes rapidly, like a cryogenic pump that cycles on and off every few seconds, RTDs might not be the best choice. But for most low-temperature applications—storage, process control, lab monitoring—RTDs’ accuracy and stability are way more important than speed. We always tell customers: if you need to track fast temperature changes, go with a thermocouple, but if you need accurate, long-term temperature data, RTD is the way to go.
Also, not all low-temperature RTDs are cryogenic-rated. Some manufacturers sell “low-temperature RTDs” that only go down to -50°C, which is fine for standard freezers or cold storage, but not for cryogenic use. That’s a critical distinction. We label our RTDs clearly: “general low-temperature” for -50°C to -200°C, and “cryogenic low-temperature” for -200°C to -270°C. Using a general low-temperature RTD in a -150°C cryo freezer will cause it to drift, and it might even fail over time. We had a customer a couple years ago who bought a batch of cheap general low RTDs from a supplier that didn’t specify the rating, and when they put them in their -120°C lab freezers, the readings were off by 4°C within a month. It cost them a whole week of research to figure out the problem, and they switched to us after that.
Now, let’s talk about best practices for using RTDs in low-temperature environments, from someone who’s spent years troubleshooting this stuff. First, calibrate your RTDs regularly. Even the most stable platinum RTDs will drift a tiny bit over time, especially if they’re exposed to rapid temperature changes. We recommend calibrating low-temperature RTDs every six months, using a reference bath that’s accurate to ±0.05°C. Don’t just trust the factory calibration—environmental factors like vibration, moisture, and thermal stress will throw things off. Second, use proper lead wiring and connections. As I mentioned earlier, thermal expansion mismatch is a big issue. We always recommend twisted, shielded lead wires to reduce electrical interference, and we solder all connections instead of crimping, because crimped connections can come loose or develop resistance changes in the cold. Third, consider the package type. If you’re installing an RTD in a tight space, like inside a small cryogenic tank, a thin-film RTD might be better than a wire-wound one. Thin-film RTDs are made by depositing a thin layer of platinum on a ceramic substrate, so they’re smaller and more flexible, and they work just as well in low temps as wire-wound ones. But if you need durability, wire-wound RTDs are stronger and less likely to break if the sensor is jostled.
At the end of the day, the answer to “Can RTD sensors be used in low-temperature environments?” is a resounding yes—if you pick the right RTD for the job. I’ve seen RTDs operate at -269°C for years without failing, deliver accurate temperature data for critical processes, and save companies millions in lost product and downtime. But the key is not just buying any RTD, it’s working with a supplier who understands the unique challenges of low-temperature environments, who designs their sensors to handle thermal stress, moisture, and extreme cold, and who can help you pick the right sensor for your specific application.
If you’re working in a low-temperature environment and you’re not sure if RTDs are the right fit, or if you’ve had issues with sensors failing or drifting in the cold, we’re here to help. We’ve designed RTDs for cryogenic storage, blast freezing, aerospace testing, and countless other low-temperature applications, and we can customize a sensor to meet your exact needs, whether you need a standard Pt100 or a custom RTD for a unique space. Don’t let a bad sensor ruin your critical work—reach out to us to discuss your low-temperature temperature monitoring requirements today.
MgO Insulated Thermocouple References
- ASTM International. (2020). Standard Specification for Industrial Resistance Thermometers. ASTM E1137-20.
- Preston-Thomas, H. (1990). The International Temperature Scale of 1990 (ITS-90). Metrologia, 27(1), 3-10.
- Zhang, Y., et al. (2018). Performance of Platinum RTDs in Cryogenic Temperatures for Space Applications. Sensors and Actuators A: Physical, 277, 456-463.
- Food and Agriculture Organization of the United Nations. (2019). Temperature Monitoring for Food Freezing and Storage. FAO Food and Nutrition Paper 118.
Chongqing Haichen Instrument Co., Ltd.
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