{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"6ES7421-7BH00-0AB0","brand":"Siemens","brandSlug":"siemens","productSlug":"6ES7421-7BH00-0AB0","canonicalUrl":"https://aoctrl.com/siemens/6ES7421-7BH00-0AB0","factsUrl":"https://aoctrl.com/api/mcp/products/6ES7421-7BH00-0AB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIMATIC S7-400 SM 421 digital input module, 6ES7421-7BH00-0AB0, 16 DI, 24V DC, optically isolated, with parameterizable input delay, diagnostic alarm, hardware interrupt.","salesMarkdown":"## What this 16-channel input module does for an S7-400 rack The Siemens 6ES7421-7BH00-0AB0 is a SIMATIC S7-400 SM 421 digital input module that gives you 16 optically isolated inputs at 24V DC. It's the go-to choice when you need to bring discrete field signals — limit switches, proximity sensors, pushbuttons — into the S7-400 backplane and you want the wiring diagnostics and interrupt handling that a basic input module doesn't offer. Each input channel accepts a signal \"1\" from 11V DC to 30V DC, with a typical current draw of 6 mA per channel. The signal \"0\" threshold is -30V DC to +5V DC, so it handles floating or slightly negative signals without false triggering — useful when you're sharing a common return with inductive loads. ## Input delay, cable length, and 2-wire sensor compatibility The input delay is parameterizable: 0.1 ms, 0.5 ms, or 3 ms. Shielded cable length at 3 ms is 1,000 m; at 0.5 ms it is 70 m; at 0.1 ms it is 30 m. Unshielded: 600 m at 3 ms, 50 m at 0.5 ms, 20 m at 0.1 ms. This module supports 2-wire proximity sensors, with a maximum permissible quiescent current of 3 mA. That means you can use standard 2-wire DC sensors without worrying about the off-state leakage falsely triggering the input — a common headache with older input cards. ## Diagnostics, interrupts, and channel isolation You get a diagnostic alarm and a hardware interrupt on this module — both are parameterizable. That means you can configure the module to generate an interrupt on a rising or falling edge, which is handy for high-speed counting or position-capture applications where you can't afford to poll the inputs. The 16 inputs are isolated in groups of 8 channels, with 500V DC isolation tested between the channels and the backplane bus. That gives you a clean separation between field wiring and the S7-400 rack, reducing the chance of a ground loop coupling noise into the backplane. ## Power budget and physical fit in the rack The module draws 130 mA from the 5V DC backplane bus and up to 120 mA from the 24V DC supply voltage L+. The 24V supply range is 20.4V to 28.8V DC, which covers the standard 24V nominal with margin for a sagging supply in a crowded cabinet.","metaTitle":"Siemens 6ES7421-7BH00-0AB0 SM 421, 16 DI, 24V DC","metaDescription":"Siemens SIMATIC S7-400 SM 421 digital input module, 16 channels, 24V DC, with parameterizable input delay, diagnostic alarm, and hardware interrupt.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Digital Input Modules"],"specifications":{"Depth":"210 mm","Width":"25 mm","Height":"290 mm","2-Wire Sensor":"Yes","For Signal \"0\"":"-30 V DC to +5 V DC","For Signal \"1\"":"11 V DC to 30 V DC","Shielded, Max.":"1 000 m; 1 000 m: 3 ms, 70 m: 0.5 ms, 30 m: 0.1 ms","Parameterizable":"Yes; 0.1 / 0.5 / 3 ms","Weight, approx.":"600 g","lifecycle_stage":"mature","Diagnostic alarm":"Yes","Rated value (DC)":"24 V","Unshielded, Max.":"600 m; 600 m: 3 ms; 50 m: 0,5 ms; 20 m: 0,1 ms","Hardware interrupt":"Yes","Diagnostics function":"Yes; Parameterizable","For Signal \"1\", Typ.":"6 mA; 6 to 8 mA","Isolation tested with":"500 V DC","Number of digital inputs":"16","from supply voltage L+, max.":"120 mA","from backplane bus 5 V DC, max.":"130 mA","Between The Channels, In Groups Of":"8","permissible range, lower limit (DC)":"20.4 V","permissible range, upper limit (DC)":"28.8 V","Between The Channels And Backplane Bus":"Yes","Permissible Quiescent Current (2-Wire Sensor), Max.":"3 mA"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$349.76 – $912.00","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=287640&mlfb=6ES7421-7BH00-0AB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/6ES7421-7BH00-0AB0/alternatives.json"},"ai":{"faq":[{"question":"Is 6ES7421-7BH00-0AB0 compatible with the S7-400 standard rack?","answer":"Yes, it is a standard-width S7-400 module (25 mm) that fits any S7-400 rack slot. It connects to the backplane bus and draws 130 mA from the 5V DC backplane supply."},{"question":"How can I order Siemens 6ES7421-7BH00-0AB0?","answer":"This module is in mature lifecycle and is sourced to order against your RFQ."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/6ES7421-7BH00-0AB0","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/6ES7421-7BH00-0AB0 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}}