SIEMENS 6ES7321-1BH50-0AA0 SM 321 16-Channel Digital Input Module | Replacement, Equivalent & Selection Guide
The SIEMENS 6ES7321-1BH50-0AA0 is a 16-channel digital input module (SM 321) designed for the SIMATIC S7-300 programmable logic controller platform. It accepts 24 V DC signals and integrates seamlessly into S7-300 racks, making it a core component in industrial automation, process control, and machine safety applications. This page provides full technical specifications, compatible replacement models, and a structured selection guide to help engineers and procurement teams make informed sourcing decisions.
Technical Specifications
- Part Number: 6ES7321-1BH50-0AA0
- Series: SIMATIC S7-300, SM 321
- Module Type: Digital Input (DI)
- Number of Inputs: 16 channels
- Input Voltage: 24 V DC
- Input Current (typical): 7 mA per channel
- Signal Groups: 2 groups of 8 channels each
- Isolation: Optocoupler isolation between field side and backplane bus
- Backplane Bus: S7-300 standard backplane
- Dimensions (W × H × D): 40 mm × 125 mm × 120 mm
- Weight: approx. 400 g
- Operating Temperature: 0 °C to +60 °C
- Storage Temperature: −40 °C to +70 °C
- Degree of Protection: IP 20
- Standards: CE, UL, cULus, ATEX (Zone 2)
- Country of Origin: Germany
Compatible Replacement & Equivalent Models
When the 6ES7321-1BH50-0AA0 is unavailable or discontinued, the following models offer functional equivalence or direct drop-in replacement capability within the S7-300 ecosystem:
- 6ES7321-1BH02-0AA0 — SM 321, 16 DI × 24 V DC, earlier hardware revision; same pinout and rack slot compatibility
- 6ES7321-1BH01-0AA0 — SM 321, 16 DI × 24 V DC, legacy revision; verify firmware compatibility with CPU
- 6ES7321-1BL00-0AA0 — SM 321, 32 DI × 24 V DC; use when higher channel density is required in the same rack
- 6ES7321-1FF01-0AA0 — SM 321, 8 DI × 120/230 V AC; select when field devices operate on AC voltage
- 6ES7321-1EH01-0AA0 — SM 321, 16 DI × 24 V DC / 48 V DC; suitable for higher-voltage DC field circuits
Note: Always verify hardware revision, firmware version, and CPU compatibility before substituting modules in a live system.
Why Choose the Original Model
- Guaranteed Compatibility: Factory-matched to SIMATIC S7-300 CPUs and ET 200M I/O stations without additional configuration
- Proven Reliability: Designed and tested to SIEMENS IEC 61131-2 standards for industrial environments
- Long-Term Support: Spare parts and firmware updates available through SIEMENS Industry Online Support (SIOS)
- Diagnostic Integration: Full diagnostic data accessible via STEP 7 / TIA Portal for predictive maintenance
- Certification Compliance: CE, UL, and ATEX Zone 2 certifications reduce re-certification burden in regulated industries
Typical Applications
- Discrete manufacturing: conveyor control, press lines, assembly stations
- Process industry: pump status monitoring, valve position feedback, level switches
- Building automation: HVAC control panels, access control integration
- Water & wastewater: pump station monitoring, flow switch inputs
- Energy & utilities: substation automation, generator control panels
- Machine tool: CNC auxiliary I/O, safety interlock circuits
System Compatibility
- Compatible CPUs: All SIMATIC S7-300 CPUs (CPU 312 through CPU 319), ET 200M with IM 153-x interface modules
- Programming Software: SIMATIC STEP 7 V5.x, TIA Portal V13 and above (with S7-300 support package)
- Rack: S7-300 standard rail (6ES7390-1AE80-0AA0 or equivalent)
- Power Supply: Requires 24 V DC load voltage from PS 307 or equivalent field power supply
- Not Compatible With: S7-400, S7-1200, S7-1500 racks (different backplane bus architecture)
Selection Guide
Use the following criteria to select the correct digital input module for your S7-300 system:
- Channel Count: 16 channels (this model) vs. 8 / 32 channels — match to your I/O point count to minimize rack slots used
- Input Voltage: 24 V DC (this model) — choose AC variants (120/230 V) only when field devices require it
- Isolation Requirement: Standard optocoupler isolation is sufficient for most applications; select isolated-per-channel variants for high-noise environments
- Diagnostic Needs: Standard SM 321 provides group diagnostics; upgrade to 6ES7321-7TH00-0AB0 for per-channel diagnostics and process interrupts
- ATEX / Hazardous Area: This module is ATEX Zone 2 rated; for Zone 1 applications, use intrinsically safe barriers with appropriate IS-rated modules
- Budget vs. New: Refurbished units are available for cost-sensitive retrofits; new units recommended for safety-critical or new installations
Quality Assurance & Sourcing
All SIEMENS modules supplied by Konmask.com are sourced through verified industrial distribution channels. Each unit undergoes:
- Visual inspection for physical damage, label authenticity, and firmware version verification
- Functional power-on test prior to shipment
- Anti-static packaging with humidity indicator cards
- Certificate of conformity available upon request
We supply new original, factory-refurbished, and tested used units — please specify your requirement when ordering.
How to Order
- Part Number: 6ES7321-1BH50-0AA0
- Minimum Order Quantity: 1 unit
- Lead Time: In-stock units ship within 1–3 business days; ex-stock orders subject to availability
- Payment: T/T, PayPal, credit card, and trade assurance accepted
- Shipping: DHL, FedEx, UPS worldwide; sea freight available for bulk orders
- RFQ: Send your BOM or part list to support@konmask.com for a competitive quote within 24 hours
Replacement & Compatibility FAQ
Q: Can 6ES7321-1BH02-0AA0 directly replace 6ES7321-1BH50-0AA0?
A: In most cases yes — both are SM 321 16 DI × 24 V DC modules with the same slot footprint. Verify the hardware revision is accepted by your CPU’s GSD/hardware catalog version in STEP 7.
Q: Is this module compatible with TIA Portal?
A: Yes. The S7-300 hardware support package in TIA Portal V13+ includes full support for SM 321 modules including 6ES7321-1BH50-0AA0.
Q: Can I use this module in an ET 200M station?
A: Yes, when paired with an IM 153-1 or IM 153-2 interface module on a standard S7-300 rail.
Q: What is the difference between -1BH50 and -1BH02 suffix?
A: The suffix indicates the hardware revision. -0AA0 is the standard commercial variant. Functional differences are minimal; consult the SIEMENS product changelog for revision-specific changes.
Q: Do you provide a warranty?
A: Yes — 12 months warranty on new original units, 6 months on refurbished units, from date of shipment.
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