Overview
The Siemens 6ES7 321-1BH02-0AA0 is a proven digital input module for the SIMATIC S7-300 PLC family. This SM 321 module accepts 16 isolated digital inputs at 24 VDC, making it a workhorse for industrial automation, process control, and machine monitoring applications. Manufactured in Germany, it delivers reliable signal acquisition from sensors, proximity switches, and pushbuttons across decades of operational use in plants worldwide.
Key Features
- 16 isolated digital inputs (DI) rated for 24 VDC nominal
- Integrated optical isolation between each group of 16 inputs
- Compatible with SIMATIC S7-300 CPU backplane via 20-pin connector
- Low power consumption: typical 3.5 W
- Status indicator LEDs per channel for diagnostics
- Proven reliability for switches, proximity sensors, and solid-state BEROs
Technical Specifications
- Module Type: SIMATIC S7-300 SM 321 Digital Input
- Input Channels: 16 DI, optically isolated in one group
- Rated Voltage: 24 VDC
- Backplane Supply Current: 10 mA @ 5 VDC (max.)
- Power Loss: 3.5 W (typical)
- Connector: 20-pin connector required
- Status Display: Green LEDs per input channel
- Manufacturing Origin: Germany
Typical Applications
- Manufacturing equipment and assembly line control
- Process automation requiring distributed sensor input
- Machine safety interlocks and limit switch monitoring
- Facility management and building automation
- Legacy system upgrades and emergency replacements
Compatibility & Replacements
The 6ES7 321-1BH02-0AA0 is a direct-fit module for any SIMATIC S7-300 system with a free slot on the backplane. It is plug-compatible with older or newer CPUs in the S7-300 range. The SIPLUS S7-300 variant (6AG1321-1BH02-2AA0) offers extended temperature operation for harsh environments. Always verify backplane connector compatibility and software configuration before installation.
