{"id":20784,"date":"2026-11-04T10:14:53","date_gmt":"2026-11-04T02:14:53","guid":{"rendered":"https:\/\/www.wehopower.com\/news\/three-wire-pt100-lead-resistance-imbalance\/"},"modified":"2026-11-04T10:14:53","modified_gmt":"2026-11-04T02:14:53","slug":"three-wire-pt100-lead-resistance-imbalance","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/","title":{"rendered":"Three-Wire Pt100 Leads: Check RTD Compensation and Wire Imbalance"},"content":{"rendered":"<div class=\"weho-geo-content\">\n<p><strong>Direct answer:<\/strong> A three-wire Pt100 circuit reduces lead-wire effects by relying on a relationship between the leads, but unequal lead resistance can leave a measurement error. Confirm the actual controller input and terminal arrangement, keep the three leads matched as the manufacturer requires, and investigate resistance imbalance before applying a display offset. Three wires do not make every cable error disappear.<\/p>\n<figure><a href=\"https:\/\/www.wehopower.com\/pl\/product\/tx4-series-tx4-s-economic-dual-display-pid-temperature-controller\/\" aria-label=\"View WEHO TX4-S product details\"><img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-scene-scene-2026-10-28-controls-ups-v1-55f30dffcd73.png\" width=\"1672\" height=\"941\" alt=\"Three-Wire Pt100 Leads: Check RTD Compensation and Wire Imbalance  title=\" three-wire pt100 leads: check rtd compensation and wire imbalance title =\"\"><\/a><figcaption>WEHO TX4-S in a temperature-control application. Application illustration; not a customer installation photo. Scene created with AI assistance; displayed values are illustrative, not field measurements. <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-scene-scene-2026-10-28-controls-ups-v1-55f30dffcd73.png\">View full-size illustration<\/a>.<\/figcaption><\/figure>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Spis tre\u015bci<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Prze\u0142\u0105cznik Spisu Tre\u015bci\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">D\u017awignia kolankowa<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#What_is_the_three-wire_assumption\" >What is the three-wire assumption?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#How_much_can_a_resistance_error_matter\" >How much can a resistance error matter?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Which_checks_belong_in_the_purchase_and_installation_record\" >Which checks belong in the purchase and installation record?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Investigate_a_reading_offset_in_a_controlled_sequence\" >Investigate a reading offset in a controlled sequence<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Identify_the_right_TX4_before_ordering\" >Identify the right TX4 before ordering<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Frequently_asked_questions\" >Frequently asked questions<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Does_equal_wire_length_guarantee_equal_resistance\" >Does equal wire length guarantee equal resistance?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.wehopower.com\/pl\/news\/three-wire-pt100-lead-resistance-imbalance\/#Should_I_correct_every_mismatch_with_a_display_offset\" >Should I correct every mismatch with a display offset?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"What_is_the_three-wire_assumption\"><\/span>What is the three-wire assumption?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>A Pt100 is a resistance temperature detector (RTD): its resistance changes with temperature. Connecting it to a controller requires lead wires, whose resistance also contributes to the measurement. A three-wire input uses its measurement arrangement to compensate for lead resistance under a matching assumption. If the relevant leads differ, compensation can leave a residual error; the exact effect depends on the controller\u2019s measurement circuit and where the mismatch occurs. <a href=\"https:\/\/www.emerson.com\/is\/content\/emerson\/en\/measurement-instrumentation\/technical\/products\/temperature\/documents\/dl-rmt-00813-0500-2654.pdf\" target=\"_blank\" rel=\"noopener\">Emerson\u2019s RTD sensor documentation<\/a> discusses three-wire compensation and the distinct four-wire approach.<\/p>\n<p>The <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2023\/11\/TX4.pdf\">WEHO TX4 manual<\/a> lists Pt100 and Cu50 RTD inputs and calls for three RTD wires of equal thickness and length. The <a href=\"https:\/\/www.wehopower.com\/pl\/product\/tx4-series-tx4-s-economic-dual-display-pid-temperature-controller\/\">TX4-S product page<\/a> also lists Pt100. Select the actual input type and consult the supplied manual for the exact model and hardware version. TX4 sizes use different terminal layouts; do not transfer terminal numbers from a different case size.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"How_much_can_a_resistance_error_matter\"><\/span>How much can a resistance error matter?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Near 0 \u00b0C, a common Pt100 with an alpha of 0.00385 has an approximate sensitivity of 0.385 \u03a9\/\u00b0C. If an independently established <em>equivalent uncorrected resistance error<\/em> were 0.2 \u03a9 at the input, its approximate temperature effect near 0 \u00b0C would be:<\/p>\n<p><strong>0.2 \u03a9 \u00f7 0.385 \u03a9\/\u00b0C \u2248 0.52 \u00b0C.<\/strong><\/p>\n<p>This is a hypothetical conversion, not a measured TX4 error or an accuracy guarantee. It does not mean that every 0.2 \u03a9 difference between any two wires produces 0.52 \u00b0C error: that depends on the input circuit and which lead differs. Sensitivity changes over the temperature range, and sensor tolerance, input accuracy, connection resistance and calibration all add to the uncertainty budget.<\/p>\n<figure><a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/technical-4.svg\"><picture><source media=\"(max-width: 560px)\" srcset=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/technical-mobile-4.svg\"><img decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/technical-4.svg\" alt=\"Three-Wire Pt100 Leads: Check RTD Compensation and Wire Imbalance  title=\" width=\"1200\" height=\"520\" three-wire pt100 leads: check rtd compensation and wire imbalance title=\"\"><\/picture><\/a><figcaption>Lead matching and a hypothetical equivalent-error conversion; this is not a wiring diagram or a product performance claim. <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/technical-4.svg\">View full-size diagram<\/a>.<\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Which_checks_belong_in_the_purchase_and_installation_record\"><\/span>Which checks belong in the purchase and installation record?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"table-scroll\">\n<table>\n<thead>\n<tr>\n<th>Przedmiot<\/th>\n<th>What to check<\/th>\n<th>Why it matters<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Controller and configuration<\/td>\n<td>Exact TX4 size, suffix, approved input setting and current manual<\/td>\n<td>Input and terminal mapping must match the installed unit.<\/td>\n<\/tr>\n<tr>\n<td>Transduktor<\/td>\n<td>Pt100 type, temperature range, tolerance and compatible three-wire arrangement<\/td>\n<td>Different RTD types and tolerances change interpretation.<\/td>\n<\/tr>\n<tr>\n<td>Lead extension<\/td>\n<td>Three matching conductors, length, material, gauge and connection quality<\/td>\n<td>Unequal resistance can defeat part of the compensation.<\/td>\n<\/tr>\n<tr>\n<td>Test record<\/td>\n<td>Reference instrument, conditions and observed readings over required range<\/td>\n<td>Shows the complete chain, not only a nominal specification.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Omron\u2019s <a href=\"https:\/\/www.ia.omron.com\/support\/faq\/answer\/53\/faq00561\/\" target=\"_blank\" rel=\"noopener\">sensor extension FAQ<\/a> addresses the importance of matching the RTD extension wires. Its instructions apply to the devices and conditions described there; follow the actual TX4 and sensor documentation for the selected assembly.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Investigate_a_reading_offset_in_a_controlled_sequence\"><\/span>Investigate a reading offset in a controlled sequence<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ol>\n<li>Record the precise sensor and controller identifiers, input setting, terminal layout, cable construction and extension length.<\/li>\n<li>Use the installation procedure to isolate power and have a qualified person inspect terminals and joints. Follow the approved measurement procedure before disconnecting an RTD.<\/li>\n<li>Measure and compare the leads using a method and instrument appropriate for low resistance; include connector and test-lead effects. Look for mismatched extensions, joints, damage or corrosion.<\/li>\n<li>Compare the installed measurement chain against a suitable reference at the relevant process conditions. If possible, check more than one temperature to distinguish a constant offset from a range-dependent error.<\/li>\n<li>Correct a verified wiring or configuration problem, then re-test. Apply any permitted offset only after the residual error is understood; an offset can conceal a changed connection and does not improve sensor tolerance.<\/li>\n<\/ol>\n<p>Do not assume that a four-wire sensor can be connected as a four-wire input to TX4, or that a controller\u2019s temperature alarm provides independent safety protection. Use only the wiring configuration and safety architecture documented for the actual installation.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Identify_the_right_TX4_before_ordering\"><\/span>Identify the right TX4 before ordering<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>TX4-S is one physical version in the TX4 family. Request the exact model, supply and output variant, current wiring instructions and Pt100 configuration from WEHO. The manufacturer product illustration below identifies the family size; it is not a view of the rear terminals or proof of a field installation.<\/p>\n<figure><a href=\"https:\/\/www.wehopower.com\/pl\/product\/tx4-series-tx4-s-economic-dual-display-pid-temperature-controller\/\"><img decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-original.png\" alt=\"Three-Wire Pt100 Leads: Check RTD Compensation and Wire Imbalance  title=\" width=\"500\" height=\"500\" three-wire pt100 leads: check rtd compensation and wire imbalance title=\"\"><\/a><figcaption>TX4-S manufacturer product illustration from the WEHO product page; use the actual unit and manual for terminal identification.<\/figcaption><\/figure>\n<figure><a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-evidence.png\"><img decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-evidence.png\" alt=\"Three-Wire Pt100 Leads: Check RTD Compensation and Wire Imbalance  title=\" width=\"1536\" height=\"1024\" three-wire pt100 leads: check rtd compensation and wire imbalance title=\"\"><\/a><figcaption>Manufacturer-published composite of actual TX4-S W1T\/R-2 product photographs. Its label indicates TC\/RTD input and default K; it does not show a Pt100 configuration, connected wiring or a completed measurement. <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/product-evidence.png\">View full-size identity evidence<\/a>.<\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Frequently_asked_questions\"><\/span>Frequently asked questions<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Does_equal_wire_length_guarantee_equal_resistance\"><\/span>Does equal wire length guarantee equal resistance?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>No. Material, gauge, joints and condition also affect resistance. Equal length and thickness are part of the manual\u2019s requirement, and the installed circuit still needs inspection and verification.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Should_I_correct_every_mismatch_with_a_display_offset\"><\/span>Should I correct every mismatch with a display offset?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>No. Find and correct the cause first; assess the remaining measurement uncertainty and verify at the relevant temperatures. An offset does not establish the integrity of a changing connection.<\/p>\n<p class=\"article-cta\">Send WEHO the TX4 size and suffix, Pt100 type, cable length and required measurement range. Request the applicable model documentation and agree on a complete-chain acceptance test. <a href=\"https:\/\/www.wehopower.com\/pl\/contact\/\">Contact WEHO<\/a>.<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Check three-wire Pt100 lead matching, residual resistance error and the correct TX4 input documentation before adjusting an offset.<\/p>","protected":false},"author":2,"featured_media":20761,"parent":0,"menu_order":37,"comment_status":"","ping_status":"","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[284],"class_list":["post-20784","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-product-articles","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/news\/20784","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/comments?post=20784"}],"version-history":[{"count":0,"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/news\/20784\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/media\/20761"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/media?parent=20784"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/pl\/wp-json\/wp\/v2\/news_category?post=20784"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}