{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"6ES7421-7DH00-0AB0","brand":"Siemens","brandSlug":"siemens","productSlug":"6ES7421-7DH00-0AB0","canonicalUrl":"https://aoctrl.com/siemens/6ES7421-7DH00-0AB0","factsUrl":"https://aoctrl.com/api/mcp/products/6ES7421-7DH00-0AB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIMATIC S7-400 SM 421, digital input module 6ES7421-7DH00-0AB0, 16 isolated inputs, UC 24-60 V AC/DC, diagnostics, alarms, wire-break detection.","salesMarkdown":"The Siemens 6ES7421-7DH00-0AB0 is a SIMATIC S7-400 SM 421 digital input module providing 16 isolated inputs accepting UC 24-60 V AC/DC — meaning it can read both 24 V DC proximity sensors and 48 V or 60 V AC limit switches from the same card without external level conversion. That voltage flexibility is the headline: it spans 24 V UC to 60 V UC (47-63 Hz), so a single module type covers the mixed-voltage field wiring common in older plants where 48 V DC panels coexist with 24 V DC control loops. The input threshold for a reliable '1' is 15-72 V DC or 15-60 V AC; '0' is -6 to +6 V DC or 0-5 V AC, giving a clean noise margin even on long cable runs. Each input is isolated channel-to-channel in groups of one, and the entire bank is isolated from the backplane bus at 1500 V AC — essential for maintaining galvanic separation when the module sits in a rack alongside high-voltage I/O or drives. The module draws up to 150 mA from the 5 V DC backplane bus and dissipates 8 W typical at 60 V DC supply, so budget that into the rack power calculation. Input filtering is parameterizable: you can set the debounce time to 0.5 ms, 3 ms, 10 ms, or 20 ms. Maximum cable length depends on that filter setting. Wire-break detection is built in: the module monitors each input for a current below 0.7 mA, which triggers a diagnostic alarm if the sensor or wiring opens. The quiescent current threshold for 2-wire sensors is adjustable between 0.5 mA and 2 mA, and the fixed current-limiting resistors for the wire-break monitoring circuit are selected automatically based on the rated voltage — 18 kΩ at 24 V, 39 kΩ at 48 V, 56 kΩ at 60 V. That means you don't need external pull-up resistors for proximity sensors; the module handles it. Diagnostic alarms and hardware interrupts are both parameterizable, so the module can signal a fault or a change-of-state directly to the CPU without polling. The status indicator per channel (green LED) gives a quick visual on each input's state; there is no red channel fault LED, but the diagnostic information is readable via the backplane bus. This module carries a lifecycle status of NRND — Not Recommended for New Designs. That means Siemens is not actively promoting it for new projects, but it remains available for existing S7-400 installations that need a spare or a last-buy. NRND status means you should secure last-buy quantities for long-term support.","metaTitle":"Siemens 6ES7421-7DH00-0AB0 SM 421 DI Module, 16 Inputs, UC 2","metaDescription":"Siemens SIMATIC S7-400 SM 421 digital input module, 16 isolated inputs, UC 24-60 V AC/DC, diagnostics, alarms, NRND — sourced to order against RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"NRND","categoryPath":["Digital Input Modules"],"specifications":{"Depth":"210 mm","Width":"25 mm","Height":"290 mm","Wire-break":"Yes; I> 0.7 mA","Rated value":"0.5 ms; 0.5 / 3 / 10 / 20 ms","2-Wire Sensor":"Yes","For Signal \"0\"":"-6 to +6 V DC/ 0 to 5 V AC","For Signal \"1\"":"15 to 72 V DC; -15 to -72 V DC; 15 to 60 V AC","Shielded, Max.":"1 000 m","Parameterizable":"Yes","Weight, approx.":"600 g","lifecycle_stage":"mature","Diagnostic alarm":"Yes; Parameterizable","Power loss, typ.":"8 W; 3.5 W (24 V DC); 6.5 W (48 V DC); 8.0 W (60 V DC)","Rated value (UC)":"24 V; 24 V UC to 60 V UC (47 ... 63 Hz)","Unshielded, Max.":"600 m; 600 m: 3, 10, 20 ms; 100 m: 0,5 ms","Hardware interrupt":"Yes; Parameterizable","Between The Channels":"Yes","Diagnostics function":"Yes; Parameterizable","For Signal \"1\", Typ.":"4 mA; 4 to 10 mA","Isolation tested with":"1 500 V AC","Type of input voltage":"AC/DC","Number of digital inputs":"16","Channel fault indicator F (red)":"No","Diagnostic information readable":"Yes; possible","from backplane bus 5 V DC, max.":"150 mA","Between The Channels, In Groups Of":"1","Between The Channels And Backplane Bus":"Yes","Status indicator digital input (green)":"Yes","Number of simultaneously controllable inputs":"16","Permissible Quiescent Current (2-Wire Sensor), Max.":"0.5 mA; 0.5 to 2 mA","Fixed current limitation for wire-break monitoring, max.":"56 kΩ; Rated voltage 60 V (50 to 72 V)","Fixed current limitation for wire-break monitoring, min.":"18 kΩ; 18 kohms: Rated voltage 24 V (15 to 35 V); 39 kohms: Rated voltage 48 V (30 to 60 V)"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$266.00 – $364.49","priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/99fa05d11deddf5c8b7401fec2fb0c88.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=510472&mlfb=6ES7421-7DH00-0AB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/6ES7421-7DH00-0AB0/alternatives.json"},"ai":{"faq":[{"question":"What is the physical size of this module?","answer":"The module is 25 mm wide, 290 mm high, and 210 mm deep, weighing approximately 600 g. It occupies a single slot in the S7-400 rack."},{"question":"How do I source this NRND module?","answer":"This module is sourced to order against an RFQ through independent distribution channels. Because it is NRND, we recommend securing last-buy quantities for long-term support of existing S7-400 racks."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/6ES7421-7DH00-0AB0","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/6ES7421-7DH00-0AB0 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-09-02T08:15:54.622Z","lastPublished":"2026-09-02T08:15:54.622Z","indexable":true}}