Siemens 6ES7221-1BH32-0XB0 SIMATIC S7-1200 SM 1221 16x24VDC Digital Input PLC I/O Module

The Siemens 6ES7221-1BH32-0XB0 is a SIMATIC S7-1200 digital input module (SM 1221) with 16 sink/source inputs rated 24 V DC, expanding a CPU rack with additional discrete inputs. Input delay is parameterizable in groups of four from 0.2 ms to 12.8 ms, and interrupt-capable channels support event-driven program response.

Technical Specifications

Certifications & Standards

• CE
• CSA
• UL
• cULus
• FM
• RCM
• KC
• Marine Approval

Selection Notes

Grouped in fours, the 16 inputs let four independent sensor groups sit on separate ground references without cross-loading, and the parameterizable input delay (0.2 ms to 12.8 ms per group) trades noise immunity against response speed — set it short for fast interrupt inputs and longer for switch or relay contacts prone to bounce. Choose the 16 DI 24V DC module over an 8-input SM 1221 variant when the station needs headroom for future sensor additions without adding another rack slot.

Applications

Expanding S7-1200 CPU input count for discrete sensors, limit switches, and pushbuttons in machine control panels, with interrupt-capable channels for fast event capture.