Siemens 6ES7421-7DH00-0AB0 SM 421 Digital Input Module S7-400

6ES7421-7DH00-0AB0 – SIMATIC S7-400 Digital Input Module

SM 421 isolated 16-channel digital input module. Supports UC 24‑60 V AC/DC. Features programmable alarms, wire‑break diagnostics, and adjustable input delays. Designed for harsh industrial environments.

Technical Specifications

Diagnostics & Alarms

• Diagnostic alarm – programmable, readable via LED.
• Hardware interrupt – configurable for fast response.
• Wire‑break detection – activates at I > 0.7 mA.
• Status indicator per channel (green LED).
• Channel fault LED (red) not available.

Environmental & Immunity

• Operating temperature: 0 °C to 60 °C.
• Storage temperature: ‑40 °C to 70 °C.
• Relative humidity: < 95 % (non‑condensing).
• EMC immunity: EN 61000‑6‑2, industrial environment.
• Vibration resistance: 5 g, 10‑150 Hz.

Installation & Commissioning

• Mounts on S7‑400 rack (U‑bus).
• Configurable via STEP 7 or TIA Portal.
• Input delay adjustable per channel (0.5/3/10/20 ms).
• Diagnostics readable online – reduces troubleshooting time.
• Front connector with screw terminals (not included).

Compatibility

• Fully compatible with SIMATIC S7‑400 CPUs (e.g., 414‑416‑417).
• Works with 2‑wire sensors (quiescent current 0.5‑2 mA).
• Supports both AC and DC input signals (47‑63 Hz).
• Integrated wire‑break monitoring for 24/48/60 V ranges.

Certifications

• CE, UL, cULus listed.
• EN 61131‑2 compliant.
• ATEX Zone 2 (optional, check marking).
• RoHS and REACH compliant.

Typical Applications

• Industrial automation & process control.
• PLC systems for manufacturing lines.
• Monitoring of 24‑60 V AC/DC sensors.
• Retrofit and upgrade of legacy S7‑400 systems.
• High‑voltage digital input acquisition.

Package & Warranty

• Package includes: Module, manual (digital), front connector not included.
• 12‑month warranty against defects.
• Technical verification before shipment.

Shipping Methods

• FedEx – Priority, International Economy.
• UPS – Express Saver, Worldwide Expedited.
• DHL – Express, Global Forwarding.

Frequently Asked Questions

• Is this module suitable for 60 V AC? Yes, rated UC 24‑60 V AC/DC.
• Can I use unshielded cable? Yes, max 600 m (delay dependent).
• Does it support wire‑break? Yes, configurable threshold.
• Is it compatible with TIA Portal? Yes, fully integrated.
• What is the input delay range? Programmable 0.5, 3, 10, 20 ms.

Why Buy From Oiltech Controls?

• 15+ years industrial automation expertise.
• Global shipment – fast, reliable logistics.
• Tested surplus & refurbished options available.
• 12‑month warranty with technical support.
• Pre‑shipment verification by engineers.
• Support for obsolete control systems.