{"id":606,"date":"2026-10-23T10:29:29","date_gmt":"2026-10-23T02:29:29","guid":{"rendered":"http:\/\/www.kurunews.com\/blog\/?p=606"},"modified":"2026-10-23T10:29:29","modified_gmt":"2026-10-23T02:29:29","slug":"what-is-the-influence-of-the-measuring-circuit-on-the-accuracy-of-a-resistance-temperatu-415c-947174","status":"publish","type":"post","link":"http:\/\/www.kurunews.com\/blog\/2026\/10\/23\/what-is-the-influence-of-the-measuring-circuit-on-the-accuracy-of-a-resistance-temperatu-415c-947174\/","title":{"rendered":"What is the influence of the measuring circuit on the accuracy of a Resistance Temperature Detector?"},"content":{"rendered":"

If you\u2019ve ever priced a Resistance Temperature Detector (RTD) from a reliable supplier, you already know they\u2019re not just a wire wrapped around a ceramic core. There\u2019s a whole lot more going on behind the scenes\u2014especially when it comes to how you connect that little sensor to your readout device. As someone who\u2019s been supplying RTDs for over a decade, I\u2019ve lost count of how many customers have come to us saying, \u201cMy RTD reads 10 degrees off\u2014why?\u201d More often than not, it\u2019s not the RTD itself that\u2019s the problem. It\u2019s the measuring circuit holding it back. Resistance Temperature Detector<\/a><\/p>\n

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Let\u2019s break this down, no fancy jargon, I promise. First, remember that RTDs work on a super simple principle: their resistance changes predictably with temperature. A standard PT100 (the most common type we supply) has 100 ohms at 0\u00b0C, and about 38.5 ohms per degree Celsius above that. But to measure that tiny change in resistance, you need a circuit that sends a small current through the RTD and measures the voltage drop across it. If that circuit isn\u2019t designed right, you get errors\u2014sometimes small, sometimes big enough to throw your whole process off.<\/p>\n

The big one most folks don\u2019t think about is lead wire resistance. If you\u2019ve got an RTD that\u2019s 10 feet away from your control panel, those two (or three, or four) wires carrying current to and from the sensor have their own resistance. Say each lead is 2 ohms. That adds 4 ohms total to your measurement, which at 0\u00b0C makes your RTD look like it\u2019s 104 ohms instead of 100. Translated to temperature? That\u2019s a ~10\u00b0C error right there, no matter how good your RTD is.<\/p>\n

Now, here\u2019s where the type of measuring circuit makes all the difference. Two-wire RTD circuits are the cheapest and most common, but they merge the RTD resistance and the lead resistance into one measurement. They work great for short distances\u2014like under 3 feet\u2014where lead resistance is negligible. But if you\u2019re running longer wires, you\u2019re eating into accuracy fast. That\u2019s why we usually steer customers toward three-wire circuits when they need sensors further out. The third wire lets the circuit measure the resistance of one lead separately and subtract it from the total, canceling out most of the lead error. Four-wire circuits take it a step further, using two leads for current and two for voltage measurement. Since the voltage leads carry almost no current, their resistance doesn\u2019t show up at all\u2014making them the most accurate, even for really long runs. But they\u2019re also pricier, so it\u2019s all about balancing your needs.<\/p>\n

Another error source is self-heating. The measuring circuit has to send current through the RTD to measure resistance, and that current makes the RTD warm up a little. If the current is too high\u2014like more than 1mA\u2014you can add a degree or two of error, especially in low-temperature or low-fluid environments where heat can\u2019t dissipate. A lot of cheap measuring circuits crank up the current to get a stronger signal, which sounds like a win but actually ruins the RTD\u2019s accuracy. We test every RTD we send with a small, optimized current (usually 0.5mA) so self-heating is under 0.1\u00b0C, but if your circuit doesn\u2019t match that, you\u2019re losing that precision.<\/p>\n

Noise is another sneaky culprit. If your RTD is in a factory with motors, variable frequency drives, or other electrical equipment, the measuring circuit picks up that electrical noise and adds it to the RTD\u2019s signal. A circuit with good filtering can cut that noise way down, but a cheap one might let a few millivolts of noise slide through\u2014enough to throw off a temperature reading, especially if you\u2019re measuring small changes. For example, a millivolt of noise on a PT100 translates to almost 3\u00b0C of error. I\u2019ve had customers come to us with RTDs that were working fine until they added a new conveyor belt near their sensor\u2014turns out the old circuit didn\u2019t have enough noise rejection, and swapping the measuring circuit fixed the problem way cheaper than replacing the RTD.<\/p>\n

Wait, let\u2019s talk about common mistakes we see all the time. A customer last year bought a batch of our high-precision PT1000s (which have 1000 ohms at 0\u00b0C, so smaller resistance changes are easier to measure) and complained they were 5\u00b0C off when installed. Turns out they used a two-wire circuit for a 15-foot run. The lead resistance was 3 ohms per wire, adding 6 ohms total, which on a PT1000 was a 0.6% error\u2014translated to 5\u00b0C. Swapping to a three-wire circuit fixed it immediately. That\u2019s not the RTD\u2019s fault; that\u2019s the circuit.<\/p>\n

Another thing: reference resistance. Some measuring circuits use a fixed resistor to calibrate the RTD\u2019s resistance. If that reference resistor is cheap or drifts over time, your accuracy goes out the window. We always recommend pairing our RTDs with circuits that have stable, calibrated reference resistors\u2014especially if you\u2019re running a process that needs tight tolerances, like food manufacturing or pharmaceutical testing. A $10 reference resistor can save you thousands in rework if your measurements are off.<\/p>\n

Now, let\u2019s get into what this means for you, as someone using an RTD. It\u2019s not enough to just buy a \u201chigh-accuracy RTD\u201d from a supplier. You have to match the measuring circuit to your setup. If you\u2019re not sure which circuit is right, here\u2019s a quick rule of thumb: under 3 feet, two-wire works. 3 to 20 feet, go three-wire. Over 20 feet, or if you need \u00b10.1\u00b0C accuracy, four-wire is non-negotiable. And always check that your circuit\u2019s current is low enough to avoid self-heating\u2014we specify on every RTD datasheet the maximum safe current, so make sure your circuit stays under that.<\/p>\n

As a supplier, we don\u2019t just ship sensors. We help customers troubleshoot when their readings are off, because we know the circuit is usually the issue. We\u2019ve seen so many folks waste money on new RTDs when all they needed was a better measuring circuit. That\u2019s why we include free guidance on circuit selection with every order, and we can even recommend compatible circuits if you\u2019re building a new system.<\/p>\n

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If you\u2019re dealing with temperature readings that feel inconsistent, or you\u2019re worried about accuracy for your next project, don\u2019t guess. Reach out to us\u2014we can walk through your setup, suggest the right RTD and matching circuit, and make sure you get the precision you need without overpaying. We\u2019ve worked with everything from small breweries needing consistent fermentation temps to large manufacturing plants monitoring industrial ovens, so we\u2019ve got the experience to help you.<\/p>\n

Smart Thermometer<\/a> References<\/p>\n

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  1. RTD Fundamentals for Temperature Measurement. Omega Engineering.<\/li>\n
  2. Resistance Temperature Detector Circuit Design Considerations. Measurement Science and Technology.<\/li>\n
  3. Lead Wire Error Compensation in RTD Circuits. Journal of Electronic Testing: Theory and Applications.<\/li>\n<\/ol>\n
    \n

    Jiangsu Zhaolong Electric Co., Ltd.<\/a>
    We’re well-known as one of the leading resistance temperature detector manufacturers and suppliers in China, featured by quality products and low price. Please feel free to buy customized resistance temperature detector made in China here from our factory. Contact us for more details.
    Address: No. 80, Zhangguo Chang’an Road, Dainan Town, Xinghua City, Jiangsu Province
    E-mail: 180193845@qq.com
    WebSite:     https:\/\/www.cnzhaolong.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    If you\u2019ve ever priced a Resistance Temperature Detector (RTD) from a reliable supplier, you already know … What is the influence of the measuring circuit on the accuracy of a Resistance Temperature Detector?<\/span>Read more<\/a><\/p>\n","protected":false},"author":353,"featured_media":606,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[569],"class_list":["post-606","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-resistance-temperature-detector-4a07-9525fe"],"_links":{"self":[{"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/posts\/606","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/users\/353"}],"replies":[{"embeddable":true,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/comments?post=606"}],"version-history":[{"count":0,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/posts\/606\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/posts\/606"}],"wp:attachment":[{"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/media?parent=606"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/categories?post=606"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.kurunews.com\/blog\/wp-json\/wp\/v2\/tags?post=606"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}