{"id":3252,"date":"2023-05-02T06:28:41","date_gmt":"2023-05-02T06:28:41","guid":{"rendered":"https:\/\/thermibel.be\/faq\/what-is-the-cvd-equation\/"},"modified":"2023-06-27T11:08:58","modified_gmt":"2023-06-27T11:08:58","slug":"what-is-the-cvd-equation","status":"publish","type":"faq","link":"https:\/\/thermibel.be\/en\/faq\/what-is-the-cvd-equation\/","title":{"rendered":"What is the CVD equation?"},"content":{"rendered":"\n<p>Pt100 sensors (platinum 100 \u03a9 (PRTD)) are more linear than thermocouples:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"480\" height=\"372\" src=\"https:\/\/thermibel.be\/app\/uploads\/2023\/05\/faq-24.png\" alt=\"\" class=\"wp-image-318\" srcset=\"https:\/\/thermibel.be\/app\/uploads\/2023\/05\/faq-24.png 480w, https:\/\/thermibel.be\/app\/uploads\/2023\/05\/faq-24-300x233.png 300w\" sizes=\"auto, (max-width: 480px) 100vw, 480px\" \/><\/figure>\n<\/div>\n\n\n<p class=\"has-text-align-center leg\">Figure 6 Change in the coefficient of linearity of a type S TC and a Pt100<\/p>\n\n\n\n<p>Figure 6 Change in the coefficient of linearity of a type S TC and a Pt100 The relationship between the temperature and the ohm value of the RTDs was calculated by Callendar, then later refined by Van Dusen, <strong>which is why it is known as the Callendar-Van Dusen (CVD) equation.<\/strong><br>$$ {R_T} = {R_0}  +  {R_0}\\alpha \\left[ {T &#8211; \\delta \\left( {\\frac{T}{{100}} &#8211; 1} \\right)\\left( {\\frac{T}{{100}}} \\right) &#8211; \\beta \\left( {\\frac{T}{{100}} &#8211; 1} \\right)\\left( {\\frac{{{T^3}}}{{100}}} \\right)} \\right] $$<\/p>\n\n\n\n<p>Where RT = resistance at T\u00b0C, R0 = resistance at 0\u00b0C, \u03b1 = temperature coefficient at 0\u00b0C in \u03a9\/\u03a9\/\u00b0C, \u03b4 = coefficient of linearisation, \u03b2 = second coefficient of linearisation for negative temperature values (\u03b2 = 0 for T &gt; 0\u00b0C).<\/p>\n\n\n\n<p>This equation has been converted to enable it to be used more easily with the coefficients A, B and C given by the standard DIN 43760 (IEC 751) and the data sheets of the components:<br>$$ {R_T} = {R_0}\\left[ {1 + AT + B{T^2} &#8211; C\\left( {T &#8211; 100} \\right){T^3}} \\right] $$<\/p>\n\n\n\n<p>C=0 for T&gt;0\u00b0C.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\" colspan=\"4\">Coefficients for different \u03b1 values<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Coefficient<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Value<\/td><td class=\"has-text-align-center\" data-align=\"center\">Value<\/td><td class=\"has-text-align-center\" data-align=\"center\">Value<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>\u03b1<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">0,003850<\/td><td class=\"has-text-align-center\" data-align=\"center\">0,003926<\/td><td class=\"has-text-align-center\" data-align=\"center\">0,003911<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>\u03b4<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">1,4999<\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>\u03b2<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">0,10863<\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>A<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">3,9083e<sup>-3<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">3,9848e<sup>-3<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">3,9692e<sup>-3<\/sup><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>B<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">-5,775e<sup>-7<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">-5,870e<sup>-7<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">-5,8495e<sup>-7<\/sup><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>C<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">-4,18301e<sup>-12<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">-4,000e<sup>-12<\/sup><\/td><td class=\"has-text-align-center\" data-align=\"center\">-4,2325e<sup>-12<\/sup><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>These three \u03b1 values represent the three main specifications for RTDs.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>0.03850 \u03a9\/\u03a9\/\u00b0C: Standards DIN 43760, IEC 751 and other international specifications, called the European Standard.<\/li>\n\n\n\n<li>0.003926 \u03a9\/\u03a9\/\u00b0C: Requires platinum of 99.999% purity or better, called the American Standard.<\/li>\n\n\n\n<li>0.3911 \u03a9\/\u03a9\/\u00b0C: Often called the US Industrial Standard.<\/li>\n<\/ul>\n","protected":false},"featured_media":0,"template":"","format":"standard","class_list":["post-3252","faq","type-faq","status-publish","format-standard","hentry"],"acf":[],"aioseo_notices":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>What is the CVD equation? - Thermibel<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/thermibel.be\/en\/faq\/what-is-the-cvd-equation\/\" \/>\n<meta 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