Proximity Sensor Wiring Diagram: How to Wire PNP, NPN, 2-Wire and 4-Wire Types<\/title>\n<\/head>\n<body>\n\n<div class=\"bd-post\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Manrope:wght@400;600;700&family=Roboto:wght@600;700&display=swap');\n\n.bd-post {\n --prose-width: 680px;\n --gap-attach: 16px;\n --gap-normal: 32px;\n --gap-section: 48px;\n --pad-compact: 16px;\n --pad-standard: 24px;\n --body-bg: #FFFFFF;\n --text-primary: #333333;\n --text-secondary: #6E6E6E;\n --heading-ink: #000000;\n --accent: #479DE2;\n --accent-deep: #2A76B4;\n --accent-hot: #FD9649;\n --accent-hot-deep: #B85C17;\n --navy: #0D3972;\n --inverse-bg: #1E1E1E;\n --inverse-text: #FFFFFF;\n --inv-secondary: #B3B3B3;\n --card-bg: #F4F8FC;\n --card-border: #E0E0E0;\n --divider-dark: #444444;\n --wire-brown: #6B4A2B;\n --wire-blue: #1F6FB2;\n --wire-black: #333333;\n --btn-white: #FFFFFF;\n --btn-ink: #1E1E1E;\n font-family: \"Manrope\", sans-serif;\n font-size: 16px;\n font-weight: 400;\n line-height: 1.6;\n color: var(--text-primary);\n background: var(--body-bg);\n padding: 40px;\n max-width: 100%;\n box-sizing: border-box;\n}\n.bd-post a { overflow-wrap: anywhere; 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}\n .bd-post .rich-table tbody tr:hover td:first-child { color: var(--accent-deep); }\n .bd-post p a, .bd-post li a, .bd-post blockquote a, .bd-post td a {\n transition: color .2s ease-out, text-decoration-color .2s ease-out;\n }\n}\n\n@media (max-width: 768px) {\n .bd-post { padding: 16px; }\n .bd-post h2 { font-size: 26px; margin-top: 32px; }\n .bd-post h3 { font-size: 20px; margin-top: 24px; }\n .bd-post .bp-1-row { flex-direction: column; align-items: flex-start; }\n .bd-post .bp-1-arrow { transform: rotate(90deg); }\n .bd-post .rich-multicol .rich-grid { grid-template-columns: 1fr; gap: 16px; }\n .bd-post .rich-multicol .rich-col:first-child {\n padding-bottom: 16px;\n border-bottom: 1px solid var(--card-border);\n }\n}\n\n\/* ---- References (canonical .bd-refs) ---- *\/\n.bd-post .bd-refs { margin: 0 0 1em; padding-left: 1.6em; }\n.bd-post .bd-refs li { font-size: 14px; line-height: 1.7; color: var(--text-secondary, #6E6E6E); margin-bottom: 10px; overflow-wrap: anywhere; }\n.bd-post .bd-refs li::marker { color: var(--accent-deep, #2A76B4); }\n.bd-post .bd-refs li a { color: var(--accent-deep, #2A76B4); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; overflow-wrap: anywhere; }\n.bd-post .bd-refs li a:hover { color: var(--heading-ink, #000000); text-decoration-thickness: 2px; }\n<\/style>\n<article class=\"bd-post-article\">\n\n<p>If you searched for a “proximity sensor wiring diagram,” you probably have one of two things in front of you. Either a brand-new sensor and an input that needs it to work, or an old sensor whose label wore off years ago. Both jobs come down to the same skill. You have to read the wiring diagram by understanding what the sensor’s output actually does, instead of memorizing one drawing and hoping it matches your unit.<\/p>\n\n<p>This guide walks the full path: the three-wire loop that every diagram shares, the output types that change how you wire it (PNP, NPN, 2-wire, 4-wire, relay), how to identify a sensor with no label and match it to your PLC input card, and what to write down before you order a replacement. Inductive, capacitive and photoelectric sensors all wire the same way. The sensing principle does not change the wiring diagram, so everything below applies across all three.<\/p>\n\n<h2>Reading a Proximity Sensor Wiring Diagram: The Three Wires and the Loop<\/h2>\n\n<p>Every DC proximity sensor diagram, no matter how cluttered, is one circuit drawn three ways: a power supply, a switch, and a load. The sensor is the switch. The only question a wiring diagram answers is where that switch sits in the circuit. For a 3-wire sensor, the answer is always printed in the same three colors.<\/p>\n\n\n<div class=\"bp-1-wires\">\n <div class=\"bp-1-row\">\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bn\">BN<\/span>\n <span><span class=\"bp-1-wire-name\">Marrom<\/span><br><span class=\"bp-1-wire-fn\">positive supply<\/span><\/span>\n <\/div>\n <span class=\"bp-1-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bu\">BU<\/span>\n <span><span class=\"bp-1-wire-name\">Azul<\/span><br><span class=\"bp-1-wire-fn\">negative supply \/ 0 V<\/span><\/span>\n <\/div>\n <span class=\"bp-1-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bk\">BK<\/span>\n <span><span class=\"bp-1-wire-name\">Preto<\/span><br><span class=\"bp-1-wire-fn\">switched output<\/span><\/span>\n <\/div>\n <\/div>\n<\/div>\n\n<p>A 3-wire DC proximity sensor has exactly three connections, standardized under EN 60947-5-2 (<a href=\"https:\/\/www.pepperl-fuchs.com\/en-us\/support\/knowledge-and-literature\/knowledge-bases-for-industrial-sensors\/knowledge-base-for-inductive-sensors\/sensor-versions\/connection-methods-gp28962\">Pepperl+Fuchs Knowledge Base<\/a>):<\/p>\n\n<ul>\n <li><strong>Brown (BN):<\/strong> positive supply<\/li>\n <li><strong>Blue (BU):<\/strong> negative supply \/ 0 V<\/li>\n <li><strong>Black (BK):<\/strong> switched output<\/li>\n<\/ul>\n\n<p>Brown and blue are the power rails; they are the same on every 3-wire sensor you will meet. The black wire is where all the action is. It is the switch output, and it does nothing on its own. A switch only works when a load sits on the other side of it. The output wire must be connected through your load (a PLC input, relay coil, or contactor) back to the <em>opposite<\/em> supply rail. A sensor with power on brown and blue but an unterminated black wire is a switch with nothing to switch.<\/p>\n\n<p>Two more things to notice before you move on. First, this color code is an EN 60947-5-2 convention, not a law of physics: old sensors, some AC types, and a minority of budget units use other colors. When the diagram and the wires disagree, trust the diagram and verify with a meter (the identification method is in the next sections). Second, if you searched for “inductive proximity sensor wiring diagram” or “photoelectric sensor wiring diagram,” stop looking for a different drawing. The sensing element (inductive coil, capacitive plate, or optical receiver) sits inside the housing and never appears in the wiring. Only the output stage does.<\/p>\n\n<h2>Output Types Decide the Wiring: 3-Wire PNP\/NPN, 2-Wire, 4-Wire, Relay<\/h2>\n\n<p>The three wires are the same in every drawing. What changes between diagrams is which rail the black output wire switches to. That is the sensor’s output type, and it is the single piece of information that determines which diagram applies to your unit.<\/p>\n\n<h3>3-Wire PNP and NPN (the type you will meet most often)<\/h3>\n\n<p>Most industrial proximity sensors sold today are 3-wire DC types, and 3-wire types come in two output flavors that share identical colors:<\/p>\n\n<ul>\n <li><strong>PNP<\/strong> (“sourcing” output): when the sensor detects its target, the black wire is switched to the <strong>positive<\/strong> rail. The output <em>sources<\/em> current into your load. The load’s other side goes to 0 V.<\/li>\n <li><strong>NPN<\/strong> (“sinking” output): when the sensor detects its target, the black wire is switched to the <strong>negative<\/strong> rail. The output <em>sinks<\/em> current from your load. The load’s other side goes to +24 V.<\/li>\n<\/ul>\n\n<p>One memory hook survives field work: <strong>P<\/strong>NP = switched <strong>P<\/strong>ositive, <strong>N<\/strong>PN = switched <strong>N<\/strong>egative. Wire colors are identical: brown to +, blue to \u2212, black to the input. If you hold a PNP drawing and an NPN drawing side by side, they differ in exactly one detail: where the far end of the load connects.<\/p>\n\n<p>Most 3-wire DC sensors accept a supply of roughly 10\u201330 V DC (check the nameplate for your unit’s range before applying power), and the vast majority ship normally open (NO). The output switches when a target enters the sensing range. Normally closed (NC) versions exist and are common in safety and anti-tie-down circuits, covered in the ordering section below.<\/p>\n\n <img decoding=\"async\" src=\"https:\/\/www.omch.com\/wp-content\/uploads\/2026\/09\/Proximity-Sensor-Wiring-Diagram-2.webp\" style=\"width: 512px; height: 384px; max-width: 100%; object-fit: cover; border-radius: 12px; margin: 30px auto; display: block; box-shadow: 10px 10px 60px 0px rgba(210, 221, 224, 0.35); transition: all 0.3s ease; cursor: pointer;\" onmouseover=\"this.style.transform='translateY(-5px) scale(1.03)'; this.style.boxShadow='15px 25px 80px 0px rgba(210, 221, 224, 0.45)'\" onmouseout=\"this.style.transform='translateY(0) scale(1)'; this.style.boxShadow='10px 10px 60px 0px rgba(210, 221, 224, 0.35)'\"> \n\n<h3>2-Wire and AC Types<\/h3>\n\n<p>A 2-wire proximity sensor has no separate output wire. The sensor’s switch is wired <strong>in series<\/strong> with the load, exactly like a limit switch or a float switch. Current flows through the sensor, through the load, and back. Power and signal share the same two wires. That series topology creates the two characteristics that catch people out:<\/p>\n\n<ul>\n <li><strong>Off-state leakage current.<\/strong> A 2-wire sensor cannot be a perfect open switch; it needs a small current to power its own electronics when “off.” That leakage is typically in the region of 1\u20132 mA (some types spec lower, some higher: check the datasheet’s <em>off-state current<\/em>). If the PLC input or relay on the other end needs less current than that to turn off, the input never sees “off,” and the sensor appears permanently on. This is the classic “2-wire sensor that never de-energizes” complaint. The standard field fix is a bleeder: a 10 k\u03a9 resistor across the input (sized for the voltage, at least 0.5 W at 24 V) so the leakage has somewhere to go.<\/li>\n <li><strong>On-state voltage drop.<\/strong> When “on,” a series device drops voltage across itself. The load receives supply voltage minus the sensor’s residual voltage, so a marginal 24 V load may underperform. Always confirm the load can tolerate the drop.<\/li>\n<\/ul>\n\n<p>DC 2-wire sensors are polarity-sensitive (reversing brown and blue destroys many units; check for built-in reverse-polarity protection). <strong>AC 2-wire sensors (typically 110\u2013240 V AC) are polarity-free.<\/strong> You can wire them in either direction, which is why old AC proximity switches are so common in retrofit work. AC types follow the same leakage-current logic, but with a triac-style output, and they are generally being replaced by DC types in new panels.<\/p>\n\n<h3>4-Wire and Relay Output<\/h3>\n\n<ul>\n <li><strong>4-wire sensors<\/strong> carry two power wires <em>and two output wires<\/em>: typically one normally-open and one normally-closed output (or in some designs, complementary PNP and NPN outputs) that switch simultaneously. Wire the pair you need; the unused output is simply left unconnected. Use a 4-wire type when your circuit genuinely needs both states: a “part present” signal to the PLC plus a “part absent” signal to an indicator, for example.<\/li>\n <li><strong>Relay-output sensors<\/strong> put a real dry contact inside the housing. The output is an isolated contact that switches AC or DC, independent of the sensor’s own supply. That isolation makes relay-output units the easiest to adapt to any input, at the price of slower response and finite mechanical life. They suit low-frequency detection (doors, positions, level) rather than high-speed counting.<\/li>\n<\/ul>\n\n<div class=\"rich-table\">\n <div class=\"table-wrapper\">\n <table>\n <caption>Which proximity sensor output type for your wiring diagram?<\/caption>\n <thead>\n <tr>\n <th scope=\"col\">Tipo de sa\u00edda<\/th>\n <th scope=\"col\">Wiring form<\/th>\n <th scope=\"col\">Pairs with<\/th>\n <th scope=\"col\">Stops working when\u2026<\/th>\n <th scope=\"col\">Check before you order<\/th>\n <\/tr>\n <\/thead>\n <tbody>\n <tr>\n <td>3-wire PNP<\/td>\n <td>BN\u2192+, BU\u2192\u2212, BK\u2192input; load returns to 0 V<\/td>\n <td>Sinking PLC inputs (most European\/US PLCs)<\/td>\n <td>The input is a sourcing type that expects the negative side switched<\/td>\n <td>Input module type code (sinking or sourcing); PNP marked on nameplate<\/td>\n <\/tr>\n <tr>\n <td>3-wire NPN<\/td>\n <td>BN\u2192+, BU\u2192\u2212, BK\u2192input; load returns to +24 V<\/td>\n <td>Sourcing PLC inputs (many Asian-built controllers)<\/td>\n <td>The input is a sinking type that expects the positive side switched; a short to ground can look like a signal<\/td>\n <td>Same; NPN marked on nameplate<\/td>\n <\/tr>\n <tr>\n <td>2-wire DC<\/td>\n <td>In series with load \u2014 no separate output<\/td>\n <td>Any input that will turn off against its leakage current<\/td>\n <td>Input’s off-state threshold is below the sensor’s leakage \u2192 false “on”<\/td>\n <td>Off-state current of sensor vs. off-state spec of the input; polarity protection<\/td>\n <\/tr>\n <tr>\n <td>2-wire AC<\/td>\n <td>In series with load, either direction<\/td>\n <td>AC input modules, contactor coils<\/td>\n <td>Inductive load switching without suppression<\/td>\n <td>Load current within sensor rating; voltage matches<\/td>\n <\/tr>\n <tr>\n <td>4-wire<\/td>\n <td>2 power + NO and NC outputs<\/td>\n <td>Two circuits needing opposite states<\/td>\n <td>Only one state wired while both are expected<\/td>\n <td>Which outputs are NO\/NC and their voltage class<\/td>\n <\/tr>\n <tr>\n <td>Relay output<\/td>\n <td>Isolated dry contact<\/td>\n <td>Any input; AC or DC load<\/td>\n <td>Switching faster than the relay’s mechanical rating<\/td>\n <td>Switching frequency; contact rating<\/td>\n <\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n<\/div>\n\n<h2>Before You Wire: Identify the Output Type and Match Your Input Card<\/h2>\n\n<p>Most wiring failures are not wiring failures. They are <em>mismatch<\/em> failures. The sensor was fine, the diagram was correct, and the two simply disagreed about which rail the output switches to. This section settles that before you power anything up: identify what your sensor is, identify what your input needs, and only then wire the two together.<\/p>\n\n<h3>Step 1 \u2014 Identify the sensor: no label? Use a meter<\/h3>\n\n<p>If the sensor has a nameplate, read the output type from it: PNP, NPN, 2-wire DC, or the manufacturer’s model code that resolves to one. If the label is worn off or the sensor came from a decommissioned line, use the two-wire test:<\/p>\n\n<ol>\n <li>Power the sensor: brown to +24 V, blue to 0 V, from a small DC supply.<\/li>\n <li>Set a multimeter to DC volts. Put the red probe on +24 V and the black probe on the black (output) wire.<\/li>\n <li>Bring a target (a steel bolt works for inductive types) to the sensing face, and read the voltage while it is detected, and again when it is not.<\/li>\n<\/ol>\n\n<p>If the reading sits near 24 V while detected and near 0 V when clear, the output pulls to the negative rail when active. That is an <strong>NPN<\/strong> unit. If it does the reverse (near 0 V when detected, near 24 V when clear), the output switches to positive. That is a <strong>PNP<\/strong> unit. A reading that never changes means either a normally-closed unit (swap the target in and out and compare) or a dead sensor. Note that an unloaded output can float ambiguously on some designs. If the readings look mushy, test with a small load (a relay coil or a PLC input) attached.<\/p>\n\n<p>Dedicated sensor testers do this automatically: connect brown, blue and black, and a PNP\/NPN indicator lights up. If you replace sensors regularly, the tester pays for itself in ten minutes of saved guessing.<\/p>\n\n<h3>Step 2 \u2014 Identify the input: sourcing or sinking, and why everyone argues about it<\/h3>\n\n<p>Here is the sentence that unlocks every PNP\/NPN argument on every forum: <strong>the sensor manufacturer names the output by its transistor (PNP or NPN), and the PLC manufacturer names the input by which current direction it accepts (sourcing or sinking). The two vocabularies describe the same pairing from opposite ends.<\/strong><\/p>\n\n<ul>\n <li>A <strong>PNP sensor<\/strong> <em>sources<\/em> current out of its black wire, so it drives a <strong>sinking<\/strong> input (current flows into the input).<\/li>\n <li>Um <strong>NPN sensor<\/strong> <em>sinks<\/em> current from its input, so it drives a <strong>sourcing<\/strong> input.<\/li>\n<\/ul>\n\n<p>“Source” and “sink” are always defined from the device you are looking at. That is why one engineer’s “sourcing sensor needs a sinking input” is another’s “sinking input module,” and why catalogs and forum posts seem to contradict each other. When a spec sheet confuses you, draw the current loop. The PNP output’s current must flow <em>into<\/em> the input card’s terminal and out the card’s common. Whatever the card calls that arrangement, if the loop closes that way, they match.<\/p>\n\n<p>In practice, regional conventions split cleanly:<\/p>\n\n<ul>\n <li><strong>Europe and North America<\/strong> standardize on PNP sensors with sinking inputs. Most Siemens S7-1200\/S7-1500 and Rockwell ControlLogix\/CompactLogix digital inputs are Type-1 sinking inputs designed for 3-wire PNP sensors (Siemens SiePortal support on S7-1200 Type 1 inputs: <a href=\"https:\/\/sieportal.siemens.com\/en-ww\/support\/forum\/posts\/digital-io-connection-to-s7-1214c\/221580\">forum reference<\/a>; Rockwell’s 1756-IB16 is a sinking input module wired to PNP-sourcing sensors per the 1756-TD002 technical data: <a href=\"https:\/\/literature.rockwellautomation.com\/idc\/groups\/literature\/documents\/td\/1756-td002_-en-e.pdf\">Rockwell literature<\/a>).<\/li>\n <li><strong>Japan and much of Asia<\/strong> standardized early on NPN sensors with sourcing inputs. Mitsubishi and Omron controllers commonly ship with input cards that expect the negative side switched. This is a legacy of the output stage costing one transistor less, not a performance difference.<\/li>\n<\/ul>\n\n<p>The one engineering caution attached to NPN: an NPN output is “on” when its transistor is closed to ground, so a short to ground on the signal wire <em>looks like a valid signal<\/em>. In circuits where a false “on” is dangerous (safety interlocks, e-stop monitoring), PNP or relay outputs are preferred. A broken or shorted wire then fails toward “off,” or is at least detectable.<\/p>\n\n\n<div class=\"bp-2-pairing\">\n <div class=\"bp-2-title\">\n <span class=\"bp-2-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M8 3 4 7l4 4\"\/><path d=\"M4 7h16\"\/><path d=\"m16 21 4-4-4-4\"\/><path d=\"M20 17H4\"\/><\/svg><\/span>\n The same circuit, named from two ends\n <\/div>\n <div class=\"bp-2-row\">\n <div class=\"bp-2-side\">\n <div class=\"bp-2-name\">PNP sensor<\/div>\n <div class=\"bp-2-desc\">output sources current out of the black wire (+V when on)<\/div>\n <\/div>\n <span class=\"bp-2-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-2-side bp-2-side--right\">\n <div class=\"bp-2-name\">Sinking input<\/div>\n <div class=\"bp-2-desc\">current flows into the input terminal<\/div>\n <\/div>\n <\/div>\n <div class=\"bp-2-row\">\n <div class=\"bp-2-side\">\n <div class=\"bp-2-name\">NPN sensor<\/div>\n <div class=\"bp-2-desc\">output sinks current from the load (0 V when on)<\/div>\n <\/div>\n <span class=\"bp-2-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-2-side bp-2-side--right\">\n <div class=\"bp-2-name\">Sourcing input<\/div>\n <div class=\"bp-2-desc\">current is supplied to the input’s common<\/div>\n <\/div>\n <\/div>\n <div class=\"bp-2-note\">Pick the pair your input card belongs to \u2014 the sensor side is named PNP or NPN, the card side is named sourcing or sinking.<\/div>\n<\/div>\n\n<h3>Step 3 \u2014 You already bought the wrong type. Field fixes, in order of permanence<\/h3>\n\n<p>Mismatches happen to everyone: a whole batch ordered PNP for a sinking card, an NPN sensor pulled from stock for a sourcing input. Three fixes exist, and they differ in how permanent they are.<\/p>\n\n<ol>\n <li><strong>Interface relay (the durable fix).<\/strong> The sensor output drives a small relay coil; the relay’s contact drives the input. A PNP output into a sourcing input, or an NPN output into a sinking input, both convert cleanly this way. Cost is one relay and a little panel space, but the conversion is electrically isolated, immune to logic-level headaches, and easy for maintenance to understand later.<\/li>\n <li><strong>Pull-up \/ pull-down resistor (the quick fix, with real limits).<\/strong> An NPN sensor into a sourcing input can be coerced with a pull-up resistor from the input terminal to +24 V; a PNP sensor into a sinking input with a pull-down to 0 V. Typical starting values are 10 k\u03a9 (0.5 W at 24 V). But this is not free: the resistor adds a permanent current load on the sensor’s output, so an undersized value overheats and destroys the output transistor over time. If you use this fix, measure the actual current, pick a resistor rated at least double the calculated dissipation, and treat it as temporary until the correct unit arrives.<\/li>\n <li><strong>Replace the input module.<\/strong> Worth it when many sensors share one card.<\/li>\n<\/ol>\n\n<p>Why does a direct mismatch usually <em>n\u00e3o<\/em> destroy anything? A PLC input’s internal impedance limits current to a safe few milliamps. The failure mode of a mismatch is “input never energizes” or “input always energizes,” not smoke. That is also why a mismatched sensor can appear dead when it is perfectly healthy. The miswire does not burn the sensor; it just never completes a circuit the input can see.<\/p>\n\n<h2>Replacing a Sensor? Seven Specs to Write Down Before You Order<\/h2>\n\n<p>Once you have identified the old sensor’s type and your input card’s requirement, ordering the replacement is where mismatches actually get <em>bought<\/em>. A sensor that matches on seven points installs in minutes. A sensor that matches on six arrives, fails, and gets shipped back. Before you order, write these down:<\/p>\n\n<div class=\"rich-checklist\">\n <p class=\"rich-title\"><span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"m3 17 2 2 4-4\"\/><path d=\"m3 7 2 2 4-4\"\/><path d=\"M13 6h8\"\/><path d=\"M13 12h8\"\/><path d=\"M13 18h8\"\/><\/svg><\/span>The seven specs on a sensor replacement order<\/p>\n <ul>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>1. Output type:<\/strong> PNP, NPN, 2-wire or relay \u2014 the #1 cause of “arrived but doesn’t work”<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>2. Output state:<\/strong> NO or NC \u2014 NO for presence\/counting, NC for safety and stop detection (NC fails toward alarm on wire break)<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>3. Supply voltage and AC\/DC:<\/strong> e.g. 10\u201330 V DC, or 110\u2013240 V AC for the old AC types<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>4. Wiring:<\/strong> 2-, 3- or 4-wire, and cable length or connector (M8\/M12) \u2014 measure the run before ordering<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>5. Sensing distance and mounting:<\/strong> e.g. 8 mm shielded vs. unshielded \u2014 shielded vs unshielded changes both distance and mounting rules<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>6. Target material:<\/strong> steel vs. aluminum\/copper for inductive types \u2014 non-ferrous targets cut sensing distance dramatically<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>7. Output logic check:<\/strong> what the input card expects (sinking\/sourcing) \u2014 write the pair, not just the sensor side<\/span><\/li>\n <\/ul>\n<\/div>\n\n<p>Walk that list line by line against the input card’s type code before you click order. Two notes. First, NC is not a preference; it is a circuit decision. In a stop-detection or guard circuit, a sensor that fails open on a broken wire is the safe direction, so NC belongs there, and NO belongs in counting and presence jobs. Second, if the old unit was 2-wire and the new one is 3-wire (or vice versa), the input wiring changes completely. A 2-wire-to-3-wire swap needs a fresh look at the input’s common wiring, not a same-position rewire.<\/p>\n\n<p>When the replacement arrives, three minutes of verification prevents a second trip. First, check the wire order against the diagram with the power off. Then power up and toggle the output into a known load: does it switch? Finally, connect it to the real input and confirm the input sees the transition, including the 2-wire leakage check from earlier if the old sensor ever “stuck on.”<\/p>\n\n\n<div class=\"bp-cta-mid\">\n <div class=\"bp-cta-mid-title\">\n <span class=\"bp-cta-mid-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"m22 2-7 20-4-9-9-4Z\"\/><path d=\"M22 2 11 13\"\/><\/svg><\/span>\n Not sure whether your sensor is PNP or NPN?\n <\/div>\n <div class=\"bp-cta-mid-sub\">Send us the drawing, the wiring diagram, or the old unit \u2014 our engineers confirm the output type before you order.<\/div>\n <a class=\"bp-cta-mid-btn\" href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_self\">Ask for a wiring match<\/a>\n<\/div>\n\n<h2>The Replacement Trade: Stocking by Output Type, Not by Brand<\/h2>\n\n<p>Every identification and ordering step above exists because of one structural fact about the maintenance business. <strong>A worn-out proximity sensor is replaced by type, not by brand.<\/strong> The machine on the plant floor does not care whose logo was molded into the failed unit. It cares that the replacement’s output type, state, voltage, wiring and sensing distance match what the original wiring diagram expects. When a label is gone and the original supplier is out of business, “type” is the only spec that can be recovered at all.<\/p>\n\n<h3>The Replacement Inquiry Is a Type Question, Not a Brand Question<\/h3>\n\n<p>For distributors and trading companies serving repair and maintenance markets, that fact rearranges the stockroom logic. The inquiry that arrives most often is not “do you sell brand X?” It is “the sensor on our wrapper machine died, help us match it.” The quote that wins that inquiry names the output type, the state, the supply, the wiring and the detection distance, and says which of the customer’s two possible input cards it suits. A quote that names only a brand and a price sends the customer to the next supplier to re-ask the question. The seven-point list above is the difference between those two quotes. That is why “write down the type” is the skill that keeps replacement orders from becoming return shipments.<\/p>\n\n<p>Stocking follows the same logic, and the regional split from the earlier section becomes an inventory decision. If your customers’ panels were built in Europe or North America, the installed base is overwhelmingly PNP with sinking inputs. Stock PNP 3-wire as the default line, with 2-wire DC and relay-output units for older machines. If your customers run Japanese or Asian-built equipment (Mitsubishi, Omron and their many compatibles), the installed base is overwhelmingly NPN with sourcing inputs, and an NPN line is the default, not a special order. Most mixed customer bases need both rails stocked, plus a small 2-wire AC shelf for the genuine legacy machines.<\/p>\n\n<div class=\"rich-multicol\">\n <div class=\"rich-grid\">\n <div class=\"rich-col\">\n <div class=\"rich-col-head\">\n <span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"M12 2a14.5 14.5 0 0 0 0 20 14.5 14.5 0 0 0 0-20\"\/><path d=\"M2 12h20\"\/><\/svg><\/span>\n Europe \/ North America installed base\n <\/div>\n <div class=\"rich-col-item\">PNP 3-wire output, sinking inputs (Siemens S7, Rockwell 1756\/1769 families)<\/div>\n <div class=\"rich-col-item\">Stock PNP as the default line; keep 2-wire DC and relay-output for older machines<\/div>\n <div class=\"rich-col-item\"><em>Quote: PNP + NO\/NC + 10\u201330 V DC + wire count + sensing distance<\/em><\/div>\n <\/div>\n <div class=\"rich-col\">\n <div class=\"rich-col-head\">\n <span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"4\"\/><path d=\"M12 2v2\"\/><path d=\"M12 20v2\"\/><path d=\"m4.93 4.93 1.41 1.41\"\/><path d=\"m17.66 17.66 1.41 1.41\"\/><path d=\"M2 12h2\"\/><path d=\"M20 12h2\"\/><path d=\"m6.34 17.66-1.41 1.41\"\/><path d=\"m19.07 4.93-1.41 1.41\"\/><\/svg><\/span>\n Asia \/ Japan installed base\n <\/div>\n <div class=\"rich-col-item\">NPN 3-wire output, sourcing inputs (Mitsubishi, Omron families)<\/div>\n <div class=\"rich-col-item\">Stock NPN as the default line; keep 2-wire DC for legacy retrofit<\/div>\n <div class=\"rich-col-item\"><em>Quote: NPN + NO\/NC + 10\u201330 V DC + wire count + sensing distance<\/em><\/div>\n <\/div>\n <\/div>\n<\/div>\n\n<h3>Stocking by Region \u2014 and Selling the Interchange Skill<\/h3>\n\n<p>There is a boundary worth stating plainly. This stocking logic fits the small-and-complete trader serving repair and small-batch markets: the customer base that orders a dozen units across many types and consolidates a container. It does not fit whole-line project supply, where an integrator buys sensors in bulk against one bill of materials. It does not fit factory-direct replenishment either. Those buyers already know their type. The replacement market is where the type knowledge lives on your side of the counter. And that knowledge, phrased as “tell me what your machine expects, and I will tell you which unit drops in,” is a service, not a catalog page. The supplier who answers the type question first gets the order. The supplier who answers only the price question gets compared.<\/p>\n\n\n<div class=\"bp-cta-end\">\n <div class=\"bp-cta-end-title\"><span class=\"bp-cta-end-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"24\" height=\"24\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><rect width=\"20\" height=\"16\" x=\"2\" y=\"4\" rx=\"2\"\/><path d=\"m22 7-8.97 5.7a1.94 1.94 0 0 1-2.06 0L2 7\"\/><\/svg><\/span>Send Your Specs, Get a Confirmed Replacement<\/div>\n <div class=\"bp-cta-end-sub\">Share the output type, state, voltage and wiring your input card needs \u2014 or send the worn unit itself \u2014 and our selection engineers verify the match before you order.<\/div>\n <a class=\"bp-cta-end-btn\" href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_self\">Talk to a selection engineer<\/a>\n<\/div>\n\n<p><em>If you are staring at a worn-label sensor or a half-legible wiring diagram right now, you do not need to solve it alone. OMCH matches replacement sensors from a brand and model number, from drawings, or from a physical sample \u2014 send us your specs or the old unit, and our selection engineers confirm the output type, state and wiring your circuit needs before you order. Start with the seven-point checklist (<a href=\"https:\/\/www.omch.com\/pt\/product-selection\/\">send it here<\/a>).<\/em><\/p>\n\n<h2>References<\/h2>\n<ol class=\"bd-refs\">\n <li>Pepperl+Fuchs. “<a href=\"https:\/\/www.pepperl-fuchs.com\/en-us\/support\/knowledge-and-literature\/knowledge-bases-for-industrial-sensors\/knowledge-base-for-inductive-sensors\/sensor-versions\/connection-methods-gp28962\" target=\"_blank\" rel=\"noopener\">Inductive sensors \u2014 electrical connections<\/a>.” Knowledge base: wire colours and plug assignment per EN 60947-5-2.<\/li>\n <li>Rockwell Automation. “<a href=\"https:\/\/literature.rockwellautomation.com\/idc\/groups\/literature\/documents\/td\/1756-td002_-en-e.pdf\" target=\"_blank\" rel=\"noopener\">1756 ControlLogix I\/O modules specifications \u2014 technical data (1756-TD002)<\/a>.” PDF: sinking input modules and PNP (sourcing) sensor wiring.<\/li>\n <li>Siemens. “<a href=\"https:\/\/sieportal.siemens.com\/en-ww\/support\/forum\/posts\/digital-io-connection-to-s7-1214c\/221580\" target=\"_blank\" rel=\"noopener\">Digital IO connection to S7-1214C<\/a>.” SiePortal support forum thread: Type 1 inputs and 3-wire sensor connection.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/product-selection\/\" target=\"_blank\" rel=\"noopener\">Sele\u00e7\u00e3o de produtos<\/a>.” Match by brand\/model, drawings or samples.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/sensor-switches\/\" target=\"_blank\" rel=\"noopener\">Chaves de sensor<\/a>.” Proximity and photoelectric families.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_blank\" rel=\"noopener\">Contato<\/a>.”<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/\" target=\"_blank\" rel=\"noopener\">Homepage<\/a>.”<\/li>\n<\/ol>\n\n<\/article>\n<\/div>\n\n<\/body>\n<\/html>\n\n\n\n<p><\/p>","protected":false},"excerpt":{"rendered":"<p>Proximity Sensor Wiring Diagram: How to Wire PNP, NPN, 2-Wire and 4-Wire Types If you searched for a “proximity sensor wiring diagram,” you probably have one of two things in front of you. Either a brand-new sensor and an input that needs it to work, or an old sensor whose label wore off years ago. […]<\/p>","protected":false},"author":4,"featured_media":12170,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Proximity Sensor Wiring Diagram: PNP, NPN & 2-Wire","_seopress_titles_desc":"Learn how to wire PNP, NPN, 2-wire, 4-wire and relay-output proximity sensors to PLC inputs. Includes wire colors, diagrams and replacement tips.","_seopress_robots_index":"","footnotes":""},"categories":[79],"tags":[],"class_list":["post-12172","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mmlblog"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/comments?post=12172"}],"version-history":[{"count":1,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172\/revisions"}],"predecessor-version":[{"id":12175,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172\/revisions\/12175"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/media\/12170"}],"wp:attachment":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/media?parent=12172"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/categories?post=12172"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/tags?post=12172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

{"id":12172,"date":"2026-09-07T02:59:37","date_gmt":"2026-09-07T02:59:37","guid":{"rendered":"https:\/\/www.omch.com\/?p=12172"},"modified":"2026-09-07T02:59:38","modified_gmt":"2026-09-07T02:59:38","slug":"proximity-sensor-wiring-diagram","status":"publish","type":"post","link":"https:\/\/www.omch.com\/pt\/proximity-sensor-wiring-diagram\/","title":{"rendered":"Proximity Sensor Wiring Diagram: PNP, NPN, 2-Wire & 4-Wire Connections"},"content":{"rendered":"\n\n\n\n\nProximity Sensor Wiring Diagram: How to Wire PNP, NPN, 2-Wire and 4-Wire Types<\/title>\n<\/head>\n<body>\n\n<div class=\"bd-post\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Manrope:wght@400;600;700&family=Roboto:wght@600;700&display=swap');\n\n.bd-post {\n --prose-width: 680px;\n --gap-attach: 16px;\n --gap-normal: 32px;\n --gap-section: 48px;\n --pad-compact: 16px;\n --pad-standard: 24px;\n --body-bg: #FFFFFF;\n --text-primary: #333333;\n --text-secondary: #6E6E6E;\n --heading-ink: #000000;\n --accent: #479DE2;\n --accent-deep: #2A76B4;\n --accent-hot: #FD9649;\n --accent-hot-deep: #B85C17;\n --navy: #0D3972;\n --inverse-bg: #1E1E1E;\n --inverse-text: #FFFFFF;\n --inv-secondary: #B3B3B3;\n --card-bg: #F4F8FC;\n --card-border: #E0E0E0;\n --divider-dark: #444444;\n --wire-brown: #6B4A2B;\n --wire-blue: #1F6FB2;\n --wire-black: #333333;\n --btn-white: #FFFFFF;\n --btn-ink: #1E1E1E;\n font-family: \"Manrope\", sans-serif;\n font-size: 16px;\n font-weight: 400;\n line-height: 1.6;\n color: var(--text-primary);\n background: var(--body-bg);\n padding: 40px;\n max-width: 100%;\n box-sizing: border-box;\n}\n.bd-post a { overflow-wrap: anywhere; 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vertical-align: -0.2em; margin-right: 8px; color: var(--accent); }\n.bd-post .bp-cta-end .bp-cta-end-title {\n font-family: \"Roboto\", sans-serif;\n font-weight: 700;\n font-size: 22px;\n line-height: 1.3;\n color: var(--inverse-text);\n}\n.bd-post .bp-cta-end .bp-cta-end-sub {\n color: var(--inv-secondary);\n font-size: 16px;\n max-width: 540px;\n}\n.bd-post .bp-cta-end-btn {\n display: inline-block;\n background: var(--accent-hot);\n color: var(--btn-ink);\n font-family: \"Manrope\", sans-serif;\n font-size: 16px;\n font-weight: 600;\n text-decoration: none;\n padding: 14px 28px;\n border-radius: 6px;\n}\n.bd-post .bp-cta-end-btn:hover {\n background: var(--btn-white);\n color: var(--navy);\n text-decoration: none;\n}\n\n\/* SANCTIONED MOTION \u2014 gated, no loops, no geometry morphs *\/\n@media (prefers-reduced-motion: no-preference) {\n .bd-post h2 {\n transition: color .2s ease-out, transform .2s ease-out;\n }\n .bd-post h2:hover {\n color: var(--accent-deep);\n transform: scale(1.02);\n }\n .bd-post .bp-1-wires, .bd-post .bp-cta-mid {\n transition: transform .2s ease-out, box-shadow .2s ease-out;\n }\n .bd-post .bp-1-wires:hover, .bd-post .bp-cta-mid:hover {\n transform: translateY(-2px);\n box-shadow: 0 6px 18px rgba(0, 0, 0, 0.08);\n }\n .bd-post .bp-cta-mid-btn, .bd-post .bp-cta-end-btn {\n transition: background-color .2s ease-out, color .2s ease-out, transform .2s ease-out;\n }\n .bd-post .bp-cta-mid-btn:hover, .bd-post .bp-cta-end-btn:hover {\n transform: translateY(-1px);\n }\n .bd-post .rich-table tbody tr td { transition: color .2s ease-out; }\n .bd-post .rich-table tbody tr:hover td:first-child { color: var(--accent-deep); }\n .bd-post p a, .bd-post li a, .bd-post blockquote a, .bd-post td a {\n transition: color .2s ease-out, text-decoration-color .2s ease-out;\n }\n}\n\n@media (max-width: 768px) {\n .bd-post { padding: 16px; }\n .bd-post h2 { font-size: 26px; margin-top: 32px; }\n .bd-post h3 { font-size: 20px; margin-top: 24px; }\n .bd-post .bp-1-row { flex-direction: column; align-items: flex-start; }\n .bd-post .bp-1-arrow { transform: rotate(90deg); }\n .bd-post .rich-multicol .rich-grid { grid-template-columns: 1fr; gap: 16px; }\n .bd-post .rich-multicol .rich-col:first-child {\n padding-bottom: 16px;\n border-bottom: 1px solid var(--card-border);\n }\n}\n\n\/* ---- References (canonical .bd-refs) ---- *\/\n.bd-post .bd-refs { margin: 0 0 1em; padding-left: 1.6em; }\n.bd-post .bd-refs li { font-size: 14px; line-height: 1.7; color: var(--text-secondary, #6E6E6E); margin-bottom: 10px; overflow-wrap: anywhere; }\n.bd-post .bd-refs li::marker { color: var(--accent-deep, #2A76B4); }\n.bd-post .bd-refs li a { color: var(--accent-deep, #2A76B4); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; overflow-wrap: anywhere; }\n.bd-post .bd-refs li a:hover { color: var(--heading-ink, #000000); text-decoration-thickness: 2px; }\n<\/style>\n<article class=\"bd-post-article\">\n\n<p>If you searched for a “proximity sensor wiring diagram,” you probably have one of two things in front of you. Either a brand-new sensor and an input that needs it to work, or an old sensor whose label wore off years ago. Both jobs come down to the same skill. You have to read the wiring diagram by understanding what the sensor’s output actually does, instead of memorizing one drawing and hoping it matches your unit.<\/p>\n\n<p>This guide walks the full path: the three-wire loop that every diagram shares, the output types that change how you wire it (PNP, NPN, 2-wire, 4-wire, relay), how to identify a sensor with no label and match it to your PLC input card, and what to write down before you order a replacement. Inductive, capacitive and photoelectric sensors all wire the same way. The sensing principle does not change the wiring diagram, so everything below applies across all three.<\/p>\n\n<h2>Reading a Proximity Sensor Wiring Diagram: The Three Wires and the Loop<\/h2>\n\n<p>Every DC proximity sensor diagram, no matter how cluttered, is one circuit drawn three ways: a power supply, a switch, and a load. The sensor is the switch. The only question a wiring diagram answers is where that switch sits in the circuit. For a 3-wire sensor, the answer is always printed in the same three colors.<\/p>\n\n\n<div class=\"bp-1-wires\">\n <div class=\"bp-1-row\">\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bn\">BN<\/span>\n <span><span class=\"bp-1-wire-name\">Marrom<\/span><br><span class=\"bp-1-wire-fn\">positive supply<\/span><\/span>\n <\/div>\n <span class=\"bp-1-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bu\">BU<\/span>\n <span><span class=\"bp-1-wire-name\">Azul<\/span><br><span class=\"bp-1-wire-fn\">negative supply \/ 0 V<\/span><\/span>\n <\/div>\n <span class=\"bp-1-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-1-wire\">\n <span class=\"bp-1-swatch bp-1-swatch--bk\">BK<\/span>\n <span><span class=\"bp-1-wire-name\">Preto<\/span><br><span class=\"bp-1-wire-fn\">switched output<\/span><\/span>\n <\/div>\n <\/div>\n<\/div>\n\n<p>A 3-wire DC proximity sensor has exactly three connections, standardized under EN 60947-5-2 (<a href=\"https:\/\/www.pepperl-fuchs.com\/en-us\/support\/knowledge-and-literature\/knowledge-bases-for-industrial-sensors\/knowledge-base-for-inductive-sensors\/sensor-versions\/connection-methods-gp28962\">Pepperl+Fuchs Knowledge Base<\/a>):<\/p>\n\n<ul>\n <li><strong>Brown (BN):<\/strong> positive supply<\/li>\n <li><strong>Blue (BU):<\/strong> negative supply \/ 0 V<\/li>\n <li><strong>Black (BK):<\/strong> switched output<\/li>\n<\/ul>\n\n<p>Brown and blue are the power rails; they are the same on every 3-wire sensor you will meet. The black wire is where all the action is. It is the switch output, and it does nothing on its own. A switch only works when a load sits on the other side of it. The output wire must be connected through your load (a PLC input, relay coil, or contactor) back to the <em>opposite<\/em> supply rail. A sensor with power on brown and blue but an unterminated black wire is a switch with nothing to switch.<\/p>\n\n<p>Two more things to notice before you move on. First, this color code is an EN 60947-5-2 convention, not a law of physics: old sensors, some AC types, and a minority of budget units use other colors. When the diagram and the wires disagree, trust the diagram and verify with a meter (the identification method is in the next sections). Second, if you searched for “inductive proximity sensor wiring diagram” or “photoelectric sensor wiring diagram,” stop looking for a different drawing. The sensing element (inductive coil, capacitive plate, or optical receiver) sits inside the housing and never appears in the wiring. Only the output stage does.<\/p>\n\n<h2>Output Types Decide the Wiring: 3-Wire PNP\/NPN, 2-Wire, 4-Wire, Relay<\/h2>\n\n<p>The three wires are the same in every drawing. What changes between diagrams is which rail the black output wire switches to. That is the sensor’s output type, and it is the single piece of information that determines which diagram applies to your unit.<\/p>\n\n<h3>3-Wire PNP and NPN (the type you will meet most often)<\/h3>\n\n<p>Most industrial proximity sensors sold today are 3-wire DC types, and 3-wire types come in two output flavors that share identical colors:<\/p>\n\n<ul>\n <li><strong>PNP<\/strong> (“sourcing” output): when the sensor detects its target, the black wire is switched to the <strong>positive<\/strong> rail. The output <em>sources<\/em> current into your load. The load’s other side goes to 0 V.<\/li>\n <li><strong>NPN<\/strong> (“sinking” output): when the sensor detects its target, the black wire is switched to the <strong>negative<\/strong> rail. The output <em>sinks<\/em> current from your load. The load’s other side goes to +24 V.<\/li>\n<\/ul>\n\n<p>One memory hook survives field work: <strong>P<\/strong>NP = switched <strong>P<\/strong>ositive, <strong>N<\/strong>PN = switched <strong>N<\/strong>egative. Wire colors are identical: brown to +, blue to \u2212, black to the input. If you hold a PNP drawing and an NPN drawing side by side, they differ in exactly one detail: where the far end of the load connects.<\/p>\n\n<p>Most 3-wire DC sensors accept a supply of roughly 10\u201330 V DC (check the nameplate for your unit’s range before applying power), and the vast majority ship normally open (NO). The output switches when a target enters the sensing range. Normally closed (NC) versions exist and are common in safety and anti-tie-down circuits, covered in the ordering section below.<\/p>\n\n <img decoding=\"async\" src=\"https:\/\/www.omch.com\/wp-content\/uploads\/2026\/09\/Proximity-Sensor-Wiring-Diagram-2.webp\" style=\"width: 512px; height: 384px; max-width: 100%; object-fit: cover; border-radius: 12px; margin: 30px auto; display: block; box-shadow: 10px 10px 60px 0px rgba(210, 221, 224, 0.35); transition: all 0.3s ease; cursor: pointer;\" onmouseover=\"this.style.transform='translateY(-5px) scale(1.03)'; this.style.boxShadow='15px 25px 80px 0px rgba(210, 221, 224, 0.45)'\" onmouseout=\"this.style.transform='translateY(0) scale(1)'; this.style.boxShadow='10px 10px 60px 0px rgba(210, 221, 224, 0.35)'\"> \n\n<h3>2-Wire and AC Types<\/h3>\n\n<p>A 2-wire proximity sensor has no separate output wire. The sensor’s switch is wired <strong>in series<\/strong> with the load, exactly like a limit switch or a float switch. Current flows through the sensor, through the load, and back. Power and signal share the same two wires. That series topology creates the two characteristics that catch people out:<\/p>\n\n<ul>\n <li><strong>Off-state leakage current.<\/strong> A 2-wire sensor cannot be a perfect open switch; it needs a small current to power its own electronics when “off.” That leakage is typically in the region of 1\u20132 mA (some types spec lower, some higher: check the datasheet’s <em>off-state current<\/em>). If the PLC input or relay on the other end needs less current than that to turn off, the input never sees “off,” and the sensor appears permanently on. This is the classic “2-wire sensor that never de-energizes” complaint. The standard field fix is a bleeder: a 10 k\u03a9 resistor across the input (sized for the voltage, at least 0.5 W at 24 V) so the leakage has somewhere to go.<\/li>\n <li><strong>On-state voltage drop.<\/strong> When “on,” a series device drops voltage across itself. The load receives supply voltage minus the sensor’s residual voltage, so a marginal 24 V load may underperform. Always confirm the load can tolerate the drop.<\/li>\n<\/ul>\n\n<p>DC 2-wire sensors are polarity-sensitive (reversing brown and blue destroys many units; check for built-in reverse-polarity protection). <strong>AC 2-wire sensors (typically 110\u2013240 V AC) are polarity-free.<\/strong> You can wire them in either direction, which is why old AC proximity switches are so common in retrofit work. AC types follow the same leakage-current logic, but with a triac-style output, and they are generally being replaced by DC types in new panels.<\/p>\n\n<h3>4-Wire and Relay Output<\/h3>\n\n<ul>\n <li><strong>4-wire sensors<\/strong> carry two power wires <em>and two output wires<\/em>: typically one normally-open and one normally-closed output (or in some designs, complementary PNP and NPN outputs) that switch simultaneously. Wire the pair you need; the unused output is simply left unconnected. Use a 4-wire type when your circuit genuinely needs both states: a “part present” signal to the PLC plus a “part absent” signal to an indicator, for example.<\/li>\n <li><strong>Relay-output sensors<\/strong> put a real dry contact inside the housing. The output is an isolated contact that switches AC or DC, independent of the sensor’s own supply. That isolation makes relay-output units the easiest to adapt to any input, at the price of slower response and finite mechanical life. They suit low-frequency detection (doors, positions, level) rather than high-speed counting.<\/li>\n<\/ul>\n\n<div class=\"rich-table\">\n <div class=\"table-wrapper\">\n <table>\n <caption>Which proximity sensor output type for your wiring diagram?<\/caption>\n <thead>\n <tr>\n <th scope=\"col\">Tipo de sa\u00edda<\/th>\n <th scope=\"col\">Wiring form<\/th>\n <th scope=\"col\">Pairs with<\/th>\n <th scope=\"col\">Stops working when\u2026<\/th>\n <th scope=\"col\">Check before you order<\/th>\n <\/tr>\n <\/thead>\n <tbody>\n <tr>\n <td>3-wire PNP<\/td>\n <td>BN\u2192+, BU\u2192\u2212, BK\u2192input; load returns to 0 V<\/td>\n <td>Sinking PLC inputs (most European\/US PLCs)<\/td>\n <td>The input is a sourcing type that expects the negative side switched<\/td>\n <td>Input module type code (sinking or sourcing); PNP marked on nameplate<\/td>\n <\/tr>\n <tr>\n <td>3-wire NPN<\/td>\n <td>BN\u2192+, BU\u2192\u2212, BK\u2192input; load returns to +24 V<\/td>\n <td>Sourcing PLC inputs (many Asian-built controllers)<\/td>\n <td>The input is a sinking type that expects the positive side switched; a short to ground can look like a signal<\/td>\n <td>Same; NPN marked on nameplate<\/td>\n <\/tr>\n <tr>\n <td>2-wire DC<\/td>\n <td>In series with load \u2014 no separate output<\/td>\n <td>Any input that will turn off against its leakage current<\/td>\n <td>Input’s off-state threshold is below the sensor’s leakage \u2192 false “on”<\/td>\n <td>Off-state current of sensor vs. off-state spec of the input; polarity protection<\/td>\n <\/tr>\n <tr>\n <td>2-wire AC<\/td>\n <td>In series with load, either direction<\/td>\n <td>AC input modules, contactor coils<\/td>\n <td>Inductive load switching without suppression<\/td>\n <td>Load current within sensor rating; voltage matches<\/td>\n <\/tr>\n <tr>\n <td>4-wire<\/td>\n <td>2 power + NO and NC outputs<\/td>\n <td>Two circuits needing opposite states<\/td>\n <td>Only one state wired while both are expected<\/td>\n <td>Which outputs are NO\/NC and their voltage class<\/td>\n <\/tr>\n <tr>\n <td>Relay output<\/td>\n <td>Isolated dry contact<\/td>\n <td>Any input; AC or DC load<\/td>\n <td>Switching faster than the relay’s mechanical rating<\/td>\n <td>Switching frequency; contact rating<\/td>\n <\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n<\/div>\n\n<h2>Before You Wire: Identify the Output Type and Match Your Input Card<\/h2>\n\n<p>Most wiring failures are not wiring failures. They are <em>mismatch<\/em> failures. The sensor was fine, the diagram was correct, and the two simply disagreed about which rail the output switches to. This section settles that before you power anything up: identify what your sensor is, identify what your input needs, and only then wire the two together.<\/p>\n\n<h3>Step 1 \u2014 Identify the sensor: no label? Use a meter<\/h3>\n\n<p>If the sensor has a nameplate, read the output type from it: PNP, NPN, 2-wire DC, or the manufacturer’s model code that resolves to one. If the label is worn off or the sensor came from a decommissioned line, use the two-wire test:<\/p>\n\n<ol>\n <li>Power the sensor: brown to +24 V, blue to 0 V, from a small DC supply.<\/li>\n <li>Set a multimeter to DC volts. Put the red probe on +24 V and the black probe on the black (output) wire.<\/li>\n <li>Bring a target (a steel bolt works for inductive types) to the sensing face, and read the voltage while it is detected, and again when it is not.<\/li>\n<\/ol>\n\n<p>If the reading sits near 24 V while detected and near 0 V when clear, the output pulls to the negative rail when active. That is an <strong>NPN<\/strong> unit. If it does the reverse (near 0 V when detected, near 24 V when clear), the output switches to positive. That is a <strong>PNP<\/strong> unit. A reading that never changes means either a normally-closed unit (swap the target in and out and compare) or a dead sensor. Note that an unloaded output can float ambiguously on some designs. If the readings look mushy, test with a small load (a relay coil or a PLC input) attached.<\/p>\n\n<p>Dedicated sensor testers do this automatically: connect brown, blue and black, and a PNP\/NPN indicator lights up. If you replace sensors regularly, the tester pays for itself in ten minutes of saved guessing.<\/p>\n\n<h3>Step 2 \u2014 Identify the input: sourcing or sinking, and why everyone argues about it<\/h3>\n\n<p>Here is the sentence that unlocks every PNP\/NPN argument on every forum: <strong>the sensor manufacturer names the output by its transistor (PNP or NPN), and the PLC manufacturer names the input by which current direction it accepts (sourcing or sinking). The two vocabularies describe the same pairing from opposite ends.<\/strong><\/p>\n\n<ul>\n <li>A <strong>PNP sensor<\/strong> <em>sources<\/em> current out of its black wire, so it drives a <strong>sinking<\/strong> input (current flows into the input).<\/li>\n <li>Um <strong>NPN sensor<\/strong> <em>sinks<\/em> current from its input, so it drives a <strong>sourcing<\/strong> input.<\/li>\n<\/ul>\n\n<p>“Source” and “sink” are always defined from the device you are looking at. That is why one engineer’s “sourcing sensor needs a sinking input” is another’s “sinking input module,” and why catalogs and forum posts seem to contradict each other. When a spec sheet confuses you, draw the current loop. The PNP output’s current must flow <em>into<\/em> the input card’s terminal and out the card’s common. Whatever the card calls that arrangement, if the loop closes that way, they match.<\/p>\n\n<p>In practice, regional conventions split cleanly:<\/p>\n\n<ul>\n <li><strong>Europe and North America<\/strong> standardize on PNP sensors with sinking inputs. Most Siemens S7-1200\/S7-1500 and Rockwell ControlLogix\/CompactLogix digital inputs are Type-1 sinking inputs designed for 3-wire PNP sensors (Siemens SiePortal support on S7-1200 Type 1 inputs: <a href=\"https:\/\/sieportal.siemens.com\/en-ww\/support\/forum\/posts\/digital-io-connection-to-s7-1214c\/221580\">forum reference<\/a>; Rockwell’s 1756-IB16 is a sinking input module wired to PNP-sourcing sensors per the 1756-TD002 technical data: <a href=\"https:\/\/literature.rockwellautomation.com\/idc\/groups\/literature\/documents\/td\/1756-td002_-en-e.pdf\">Rockwell literature<\/a>).<\/li>\n <li><strong>Japan and much of Asia<\/strong> standardized early on NPN sensors with sourcing inputs. Mitsubishi and Omron controllers commonly ship with input cards that expect the negative side switched. This is a legacy of the output stage costing one transistor less, not a performance difference.<\/li>\n<\/ul>\n\n<p>The one engineering caution attached to NPN: an NPN output is “on” when its transistor is closed to ground, so a short to ground on the signal wire <em>looks like a valid signal<\/em>. In circuits where a false “on” is dangerous (safety interlocks, e-stop monitoring), PNP or relay outputs are preferred. A broken or shorted wire then fails toward “off,” or is at least detectable.<\/p>\n\n\n<div class=\"bp-2-pairing\">\n <div class=\"bp-2-title\">\n <span class=\"bp-2-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M8 3 4 7l4 4\"\/><path d=\"M4 7h16\"\/><path d=\"m16 21 4-4-4-4\"\/><path d=\"M20 17H4\"\/><\/svg><\/span>\n The same circuit, named from two ends\n <\/div>\n <div class=\"bp-2-row\">\n <div class=\"bp-2-side\">\n <div class=\"bp-2-name\">PNP sensor<\/div>\n <div class=\"bp-2-desc\">output sources current out of the black wire (+V when on)<\/div>\n <\/div>\n <span class=\"bp-2-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-2-side bp-2-side--right\">\n <div class=\"bp-2-name\">Sinking input<\/div>\n <div class=\"bp-2-desc\">current flows into the input terminal<\/div>\n <\/div>\n <\/div>\n <div class=\"bp-2-row\">\n <div class=\"bp-2-side\">\n <div class=\"bp-2-name\">NPN sensor<\/div>\n <div class=\"bp-2-desc\">output sinks current from the load (0 V when on)<\/div>\n <\/div>\n <span class=\"bp-2-arrow\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"M5 12h14\"\/><path d=\"m12 5 7 7-7 7\"\/><\/svg><\/span>\n <div class=\"bp-2-side bp-2-side--right\">\n <div class=\"bp-2-name\">Sourcing input<\/div>\n <div class=\"bp-2-desc\">current is supplied to the input’s common<\/div>\n <\/div>\n <\/div>\n <div class=\"bp-2-note\">Pick the pair your input card belongs to \u2014 the sensor side is named PNP or NPN, the card side is named sourcing or sinking.<\/div>\n<\/div>\n\n<h3>Step 3 \u2014 You already bought the wrong type. Field fixes, in order of permanence<\/h3>\n\n<p>Mismatches happen to everyone: a whole batch ordered PNP for a sinking card, an NPN sensor pulled from stock for a sourcing input. Three fixes exist, and they differ in how permanent they are.<\/p>\n\n<ol>\n <li><strong>Interface relay (the durable fix).<\/strong> The sensor output drives a small relay coil; the relay’s contact drives the input. A PNP output into a sourcing input, or an NPN output into a sinking input, both convert cleanly this way. Cost is one relay and a little panel space, but the conversion is electrically isolated, immune to logic-level headaches, and easy for maintenance to understand later.<\/li>\n <li><strong>Pull-up \/ pull-down resistor (the quick fix, with real limits).<\/strong> An NPN sensor into a sourcing input can be coerced with a pull-up resistor from the input terminal to +24 V; a PNP sensor into a sinking input with a pull-down to 0 V. Typical starting values are 10 k\u03a9 (0.5 W at 24 V). But this is not free: the resistor adds a permanent current load on the sensor’s output, so an undersized value overheats and destroys the output transistor over time. If you use this fix, measure the actual current, pick a resistor rated at least double the calculated dissipation, and treat it as temporary until the correct unit arrives.<\/li>\n <li><strong>Replace the input module.<\/strong> Worth it when many sensors share one card.<\/li>\n<\/ol>\n\n<p>Why does a direct mismatch usually <em>n\u00e3o<\/em> destroy anything? A PLC input’s internal impedance limits current to a safe few milliamps. The failure mode of a mismatch is “input never energizes” or “input always energizes,” not smoke. That is also why a mismatched sensor can appear dead when it is perfectly healthy. The miswire does not burn the sensor; it just never completes a circuit the input can see.<\/p>\n\n<h2>Replacing a Sensor? Seven Specs to Write Down Before You Order<\/h2>\n\n<p>Once you have identified the old sensor’s type and your input card’s requirement, ordering the replacement is where mismatches actually get <em>bought<\/em>. A sensor that matches on seven points installs in minutes. A sensor that matches on six arrives, fails, and gets shipped back. Before you order, write these down:<\/p>\n\n<div class=\"rich-checklist\">\n <p class=\"rich-title\"><span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"m3 17 2 2 4-4\"\/><path d=\"m3 7 2 2 4-4\"\/><path d=\"M13 6h8\"\/><path d=\"M13 12h8\"\/><path d=\"M13 18h8\"\/><\/svg><\/span>The seven specs on a sensor replacement order<\/p>\n <ul>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>1. Output type:<\/strong> PNP, NPN, 2-wire or relay \u2014 the #1 cause of “arrived but doesn’t work”<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>2. Output state:<\/strong> NO or NC \u2014 NO for presence\/counting, NC for safety and stop detection (NC fails toward alarm on wire break)<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>3. Supply voltage and AC\/DC:<\/strong> e.g. 10\u201330 V DC, or 110\u2013240 V AC for the old AC types<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>4. Wiring:<\/strong> 2-, 3- or 4-wire, and cable length or connector (M8\/M12) \u2014 measure the run before ordering<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>5. Sensing distance and mounting:<\/strong> e.g. 8 mm shielded vs. unshielded \u2014 shielded vs unshielded changes both distance and mounting rules<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>6. Target material:<\/strong> steel vs. aluminum\/copper for inductive types \u2014 non-ferrous targets cut sensing distance dramatically<\/span><\/li>\n <li><span class=\"rich-item-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"m9 12 2 2 4-4\"\/><\/svg><\/span><span><strong>7. Output logic check:<\/strong> what the input card expects (sinking\/sourcing) \u2014 write the pair, not just the sensor side<\/span><\/li>\n <\/ul>\n<\/div>\n\n<p>Walk that list line by line against the input card’s type code before you click order. Two notes. First, NC is not a preference; it is a circuit decision. In a stop-detection or guard circuit, a sensor that fails open on a broken wire is the safe direction, so NC belongs there, and NO belongs in counting and presence jobs. Second, if the old unit was 2-wire and the new one is 3-wire (or vice versa), the input wiring changes completely. A 2-wire-to-3-wire swap needs a fresh look at the input’s common wiring, not a same-position rewire.<\/p>\n\n<p>When the replacement arrives, three minutes of verification prevents a second trip. First, check the wire order against the diagram with the power off. Then power up and toggle the output into a known load: does it switch? Finally, connect it to the real input and confirm the input sees the transition, including the 2-wire leakage check from earlier if the old sensor ever “stuck on.”<\/p>\n\n\n<div class=\"bp-cta-mid\">\n <div class=\"bp-cta-mid-title\">\n <span class=\"bp-cta-mid-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><path d=\"m22 2-7 20-4-9-9-4Z\"\/><path d=\"M22 2 11 13\"\/><\/svg><\/span>\n Not sure whether your sensor is PNP or NPN?\n <\/div>\n <div class=\"bp-cta-mid-sub\">Send us the drawing, the wiring diagram, or the old unit \u2014 our engineers confirm the output type before you order.<\/div>\n <a class=\"bp-cta-mid-btn\" href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_self\">Ask for a wiring match<\/a>\n<\/div>\n\n<h2>The Replacement Trade: Stocking by Output Type, Not by Brand<\/h2>\n\n<p>Every identification and ordering step above exists because of one structural fact about the maintenance business. <strong>A worn-out proximity sensor is replaced by type, not by brand.<\/strong> The machine on the plant floor does not care whose logo was molded into the failed unit. It cares that the replacement’s output type, state, voltage, wiring and sensing distance match what the original wiring diagram expects. When a label is gone and the original supplier is out of business, “type” is the only spec that can be recovered at all.<\/p>\n\n<h3>The Replacement Inquiry Is a Type Question, Not a Brand Question<\/h3>\n\n<p>For distributors and trading companies serving repair and maintenance markets, that fact rearranges the stockroom logic. The inquiry that arrives most often is not “do you sell brand X?” It is “the sensor on our wrapper machine died, help us match it.” The quote that wins that inquiry names the output type, the state, the supply, the wiring and the detection distance, and says which of the customer’s two possible input cards it suits. A quote that names only a brand and a price sends the customer to the next supplier to re-ask the question. The seven-point list above is the difference between those two quotes. That is why “write down the type” is the skill that keeps replacement orders from becoming return shipments.<\/p>\n\n<p>Stocking follows the same logic, and the regional split from the earlier section becomes an inventory decision. If your customers’ panels were built in Europe or North America, the installed base is overwhelmingly PNP with sinking inputs. Stock PNP 3-wire as the default line, with 2-wire DC and relay-output units for older machines. If your customers run Japanese or Asian-built equipment (Mitsubishi, Omron and their many compatibles), the installed base is overwhelmingly NPN with sourcing inputs, and an NPN line is the default, not a special order. Most mixed customer bases need both rails stocked, plus a small 2-wire AC shelf for the genuine legacy machines.<\/p>\n\n<div class=\"rich-multicol\">\n <div class=\"rich-grid\">\n <div class=\"rich-col\">\n <div class=\"rich-col-head\">\n <span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"10\"\/><path d=\"M12 2a14.5 14.5 0 0 0 0 20 14.5 14.5 0 0 0 0-20\"\/><path d=\"M2 12h20\"\/><\/svg><\/span>\n Europe \/ North America installed base\n <\/div>\n <div class=\"rich-col-item\">PNP 3-wire output, sinking inputs (Siemens S7, Rockwell 1756\/1769 families)<\/div>\n <div class=\"rich-col-item\">Stock PNP as the default line; keep 2-wire DC and relay-output for older machines<\/div>\n <div class=\"rich-col-item\"><em>Quote: PNP + NO\/NC + 10\u201330 V DC + wire count + sensing distance<\/em><\/div>\n <\/div>\n <div class=\"rich-col\">\n <div class=\"rich-col-head\">\n <span class=\"rich-title-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><circle cx=\"12\" cy=\"12\" r=\"4\"\/><path d=\"M12 2v2\"\/><path d=\"M12 20v2\"\/><path d=\"m4.93 4.93 1.41 1.41\"\/><path d=\"m17.66 17.66 1.41 1.41\"\/><path d=\"M2 12h2\"\/><path d=\"M20 12h2\"\/><path d=\"m6.34 17.66-1.41 1.41\"\/><path d=\"m19.07 4.93-1.41 1.41\"\/><\/svg><\/span>\n Asia \/ Japan installed base\n <\/div>\n <div class=\"rich-col-item\">NPN 3-wire output, sourcing inputs (Mitsubishi, Omron families)<\/div>\n <div class=\"rich-col-item\">Stock NPN as the default line; keep 2-wire DC for legacy retrofit<\/div>\n <div class=\"rich-col-item\"><em>Quote: NPN + NO\/NC + 10\u201330 V DC + wire count + sensing distance<\/em><\/div>\n <\/div>\n <\/div>\n<\/div>\n\n<h3>Stocking by Region \u2014 and Selling the Interchange Skill<\/h3>\n\n<p>There is a boundary worth stating plainly. This stocking logic fits the small-and-complete trader serving repair and small-batch markets: the customer base that orders a dozen units across many types and consolidates a container. It does not fit whole-line project supply, where an integrator buys sensors in bulk against one bill of materials. It does not fit factory-direct replenishment either. Those buyers already know their type. The replacement market is where the type knowledge lives on your side of the counter. And that knowledge, phrased as “tell me what your machine expects, and I will tell you which unit drops in,” is a service, not a catalog page. The supplier who answers the type question first gets the order. The supplier who answers only the price question gets compared.<\/p>\n\n\n<div class=\"bp-cta-end\">\n <div class=\"bp-cta-end-title\"><span class=\"bp-cta-end-ico\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"24\" height=\"24\" viewbox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"><rect width=\"20\" height=\"16\" x=\"2\" y=\"4\" rx=\"2\"\/><path d=\"m22 7-8.97 5.7a1.94 1.94 0 0 1-2.06 0L2 7\"\/><\/svg><\/span>Send Your Specs, Get a Confirmed Replacement<\/div>\n <div class=\"bp-cta-end-sub\">Share the output type, state, voltage and wiring your input card needs \u2014 or send the worn unit itself \u2014 and our selection engineers verify the match before you order.<\/div>\n <a class=\"bp-cta-end-btn\" href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_self\">Talk to a selection engineer<\/a>\n<\/div>\n\n<p><em>If you are staring at a worn-label sensor or a half-legible wiring diagram right now, you do not need to solve it alone. OMCH matches replacement sensors from a brand and model number, from drawings, or from a physical sample \u2014 send us your specs or the old unit, and our selection engineers confirm the output type, state and wiring your circuit needs before you order. Start with the seven-point checklist (<a href=\"https:\/\/www.omch.com\/pt\/product-selection\/\">send it here<\/a>).<\/em><\/p>\n\n<h2>References<\/h2>\n<ol class=\"bd-refs\">\n <li>Pepperl+Fuchs. “<a href=\"https:\/\/www.pepperl-fuchs.com\/en-us\/support\/knowledge-and-literature\/knowledge-bases-for-industrial-sensors\/knowledge-base-for-inductive-sensors\/sensor-versions\/connection-methods-gp28962\" target=\"_blank\" rel=\"noopener\">Inductive sensors \u2014 electrical connections<\/a>.” Knowledge base: wire colours and plug assignment per EN 60947-5-2.<\/li>\n <li>Rockwell Automation. “<a href=\"https:\/\/literature.rockwellautomation.com\/idc\/groups\/literature\/documents\/td\/1756-td002_-en-e.pdf\" target=\"_blank\" rel=\"noopener\">1756 ControlLogix I\/O modules specifications \u2014 technical data (1756-TD002)<\/a>.” PDF: sinking input modules and PNP (sourcing) sensor wiring.<\/li>\n <li>Siemens. “<a href=\"https:\/\/sieportal.siemens.com\/en-ww\/support\/forum\/posts\/digital-io-connection-to-s7-1214c\/221580\" target=\"_blank\" rel=\"noopener\">Digital IO connection to S7-1214C<\/a>.” SiePortal support forum thread: Type 1 inputs and 3-wire sensor connection.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/product-selection\/\" target=\"_blank\" rel=\"noopener\">Sele\u00e7\u00e3o de produtos<\/a>.” Match by brand\/model, drawings or samples.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/sensor-switches\/\" target=\"_blank\" rel=\"noopener\">Chaves de sensor<\/a>.” Proximity and photoelectric families.<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/contact\/\" target=\"_blank\" rel=\"noopener\">Contato<\/a>.”<\/li>\n <li>OMCH. “<a href=\"https:\/\/www.omch.com\/pt\/\" target=\"_blank\" rel=\"noopener\">Homepage<\/a>.”<\/li>\n<\/ol>\n\n<\/article>\n<\/div>\n\n<\/body>\n<\/html>\n\n\n\n<p><\/p>","protected":false},"excerpt":{"rendered":"<p>Proximity Sensor Wiring Diagram: How to Wire PNP, NPN, 2-Wire and 4-Wire Types If you searched for a “proximity sensor wiring diagram,” you probably have one of two things in front of you. Either a brand-new sensor and an input that needs it to work, or an old sensor whose label wore off years ago. […]<\/p>","protected":false},"author":4,"featured_media":12170,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Proximity Sensor Wiring Diagram: PNP, NPN & 2-Wire","_seopress_titles_desc":"Learn how to wire PNP, NPN, 2-wire, 4-wire and relay-output proximity sensors to PLC inputs. Includes wire colors, diagrams and replacement tips.","_seopress_robots_index":"","footnotes":""},"categories":[79],"tags":[],"class_list":["post-12172","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mmlblog"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/comments?post=12172"}],"version-history":[{"count":1,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172\/revisions"}],"predecessor-version":[{"id":12175,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/posts\/12172\/revisions\/12175"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/media\/12170"}],"wp:attachment":[{"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/media?parent=12172"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/categories?post=12172"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.omch.com\/pt\/wp-json\/wp\/v2\/tags?post=12172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}