Current Sinking DC Input Solution – Allen-Bradley 1746-IH16 | SLC 500 Series
In high-density discrete manufacturing environments, engineers face a persistent challenge: field sensors wired with sinking outputs (NPN) must interface reliably with PLC input cards under fluctuating supply voltages, electrical noise, and ambient temperatures that can swing from −20 °C to +60 °C. A single mismatched input module causes nuisance trips, false reads, or complete line stoppages — in automotive body shops, for example, unplanned downtime costs an average of $22,000 per minute. With 16 channels per slot, even one channel failure can cascade across an entire cell.
The Allen-Bradley 1746-IH16 eliminates this risk by providing 16 independently isolated current-sinking (Type 1 IEC 61131-2) DC input channels rated 10–30 VDC, with a guaranteed ON-state current threshold of ≥ 2 mA and OFF-state leakage tolerance of ≤ 1.5 mA. Designed natively for the SLC 500 backplane, it draws only 85 mA from the 5 VDC bus, preserving power budget for high-channel-count racks. The result: deterministic, noise-immune signal acquisition from proximity sensors, photoelectric eyes, limit switches, and pushbuttons — without external signal conditioning.
Where This Product Is Used
Automotive Body & Assembly
• Weld gun confirmation via inductive proximity sensors (NPN/sinking) in 480 VAC weld cells — 1746-IH16 handles 24 VDC logic isolated from high-voltage interference
• Fixture clamp-open / clamp-closed limit switch feedback on transfer lines running at 60 parts/hour
• Door interlock and light curtain OSSD monitoring where IEC 61131-2 Type 1 compliance is mandated by OSHA 1910.217
Food & Beverage Processing
• Capacitive level sensors on stainless steel tanks in washdown zones (IP65 enclosures, 40 °C ambient) — module’s 30 VDC max rating matches 24 VDC PELV circuits required by FDA 21 CFR Part 117
• Conveyor jam detection via photoelectric diffuse sensors at 120 m/min belt speeds
• CIP (Clean-In-Place) valve position feedback where signal integrity must be maintained through caustic spray cycles
Oil & Gas / Petrochemical
• Wellhead pump run/stop status from 2-wire proximity sensors in Class I Div 2 panels (module installed in safe area; field barriers handle hazardous zone isolation)
• Pipeline pig detector switches with cable runs exceeding 300 m — module’s ≥ 2 mA ON threshold accommodates voltage drop on long cable runs
• Compressor vibration switch inputs where false triggering must be eliminated per API 670 machinery protection standards
Pharmaceutical / Life Sciences
• Isolator glove port interlock monitoring under 21 CFR Part 11 audit trail requirements
• Lyophilizer door and shelf position sensing in −50 °C chamber environments (module in climate-controlled MCC room)
• Autoclave cycle-complete signal acquisition where IQ/OQ/PQ validation demands documented module specifications
Material Handling & Warehousing
• Pallet presence detection on AS/RS (Automated Storage and Retrieval Systems) with 500+ sensor nodes per zone
• Sorter divert confirmation at 2,000 packages/hour — 1746-IH16’s 8 ms input filter eliminates bounce from mechanical divert gates
• AGV (Automated Guided Vehicle) docking position sensors in 24/7 distribution centers
Water & Wastewater Treatment
• Pump seal failure detection via float switches in wet wells (4–20 mA transmitters handled separately; discrete dry contacts feed 1746-IH16)
• UV disinfection lamp status monitoring per EPA 40 CFR Part 141 compliance logging
• Valve open/close limit feedback on SCADA-integrated treatment trains with 10–15 year lifecycle expectations
Technical Specifications
| Parameter | Value | Application Relevance |
|---|---|---|
| Module Type | Current Sinking (Type 1, IEC 61131-2) | Compatible with NPN/sinking field sensors — the dominant wiring standard in Asian and European OEM equipment |
| Number of Inputs | 16 channels | Maximizes I/O density per slot; reduces rack cost vs. 8-channel alternatives |
| Input Voltage Range | 10–30 VDC | Accommodates 24 VDC ±20% supply variation without false reads |
| ON-State Voltage | ≥ 10 VDC | Ensures reliable turn-on even with long cable runs and connector resistance |
| OFF-State Voltage | ≤ 5 VDC | Prevents false ON from leakage current in parallel sensor wiring |
| ON-State Current | ≥ 2 mA | Sufficient to drive solid-state sensor outputs; compatible with 2-wire sensors |
| OFF-State Current | ≤ 1.5 mA | Rejects leakage from 2-wire sensors without external bleeder resistors |
| Input Impedance | 5.6 kΩ | Limits inrush current; protects sensor output stages |
| Input Filter Time | 8 ms (hardware) | Eliminates contact bounce from mechanical limit switches and pushbuttons |
| Backplane Current (5 VDC) | 85 mA | Low power draw preserves budget in fully loaded 13-slot racks |
| Backplane Current (24 VDC) | 0 mA | No 24 VDC backplane load — simplifies power supply sizing |
| Operating Temperature | 0 °C to +60 °C | Covers standard MCC and control panel environments without derating |
| Storage Temperature | −40 °C to +85 °C | Safe for unheated warehouse storage and cold-climate shipping |
| Relative Humidity | 5–95% non-condensing | Suitable for food processing and coastal installations |
| Isolation | Group isolation (8 channels per common) | Limits fault propagation; allows mixed-voltage field wiring in two groups |
| Indicators | 16 × green LED (one per channel) | Enables rapid field diagnostics without laptop or handheld programmer |
| Slot Width | Single slot | Fits all SLC 500 fixed and modular chassis (1746-A4 through 1746-A13) |
| Weight | ~300 g | Standard for SLC 500 I/O modules |
| Certifications | UL, CSA, CE, C-Tick | Accepted by AHJ in North America, EU, and Australia/New Zealand |
Why Engineers Specify This Model
- In automotive weld cell applications, the 1746-IH16 delivers noise-immune signal acquisition because its 5.6 kΩ input impedance and group isolation architecture reject common-mode interference from 480 VAC weld transformers, meeting IEC 61000-4-4 Level 3 EFT immunity requirements.
- In food processing washdown environments, the 1746-IH16 delivers reliable 24/7 operation because its 10–30 VDC input range accommodates PELV circuit voltage variations without nuisance trips, meeting FDA 21 CFR Part 117 hygienic equipment control requirements.
- In long-cable-run oil & gas installations, the 1746-IH16 delivers dependable ON-state detection because its ≥ 2 mA threshold accommodates up to 12 Ω cable resistance at 24 VDC, meeting API 670 signal integrity requirements for machinery protection systems.
- In pharmaceutical isolator and autoclave control, the 1746-IH16 delivers documented, validated performance because its published specifications support IQ/OQ/PQ protocols, meeting 21 CFR Part 11 and EU Annex 11 validation documentation requirements.
- In high-speed material handling sorters, the 1746-IH16 delivers bounce-free input reads because its 8 ms hardware input filter eliminates mechanical contact chatter at 2,000+ cycles/hour, meeting ANSI/RIA R15.06 safety system reliability requirements.
- In water treatment SCADA systems, the 1746-IH16 delivers decade-long service life because Allen-Bradley’s SLC 500 platform has a published 10+ year parts availability commitment, meeting EPA 40 CFR Part 141 infrastructure longevity requirements for municipal water systems.
Complete System Bill of Materials
- 1746-IH16 (this module) — 16-channel current sinking DC input; the primary signal acquisition device
- SLC 500 Chassis (e.g., 1746-A4, 1746-A7, 1746-A10, 1746-A13) — backplane carrier; slot count determines maximum I/O capacity
- SLC 5/03, 5/04, or 5/05 Processor (e.g., 1747-L531, 1747-L541, 1747-L551) — CPU; 5/05 adds Ethernet for SCADA integration
- Power Supply (e.g., 1746-P1, 1746-P2, 1746-P4) — 5 VDC/24 VDC backplane power; P4 recommended for fully loaded 13-slot racks
- 24 VDC Field Power Supply (e.g., Allen-Bradley 1606-XLP, Phoenix Contact QUINT) — powers field sensors; sized at 1.5× calculated sensor load
- 1492-IFM Series Interface Module — DIN-rail terminal block interface; eliminates direct field wiring to module connector, simplifying maintenance
- 1492-CABLE Series Pre-wired Cable — 40-pin to 1492-IFM; eliminates field wiring errors and reduces commissioning time by ~60%
- 1747-UIC USB-to-DH485 Interface — programming cable for RSLogix 500 / Studio 5000 Logix Designer connection
- Inductive Proximity Sensors (NPN/sinking output, 10–30 VDC, M12 or M18) — typical field devices; confirm sinking output type matches 1746-IH16 input type
- Surge Protection Devices (e.g., Phoenix Contact TT-UKK5-D) — field cable surge arrestors; recommended for outdoor or long-run installations per IEC 61643-21
Compliance & Industry Standards
- UL 508 (Underwriters Laboratories) — Industrial Control Equipment listing; required by most North American AHJs for panel approval and insurance compliance
- CSA C22.2 No. 142 (Canadian Standards Association) — Process Control Equipment; mandatory for installations in Canadian jurisdictions
- CE Marking / EN 61131-2 (European Commission) — Programmable Controllers Part 2: Equipment Requirements; required for CE-marked machinery exported to EU/EEA markets
- IEC 61131-2 Type 1 Input (International Electrotechnical Commission) — defines ON/OFF voltage and current thresholds; ensures interoperability with IEC-compliant field sensors globally
- C-Tick / RCM (Australian Communications and Media Authority) — EMC compliance mark; required for sale and installation in Australia and New Zealand
- RoHS Compliant (EU Directive 2011/65/EU) — restricts hazardous substances; required for CE marking and preferred by environmentally conscious procurement teams
Quality Assurance & Sourcing
Sourcing Channels: Konmask.com sources the 1746-IH16 exclusively through authorized Allen-Bradley distributors, certified surplus dealers with documented chain-of-custody, and direct OEM decommission programs. We do not source from anonymous brokers or unverified secondary markets.
4-Step Inspection Process:
- Visual & Physical Inspection — Label authenticity, connector pin condition, housing integrity, and date code verification against Rockwell Automation production records
- Functional Bench Test — Each channel activated with calibrated 24 VDC test signal; ON/OFF thresholds verified against published specifications; LED indicator function confirmed
- Backplane Communication Test — Module installed in SLC 500 test rack; RSLogix 500 I/O configuration verified; no fault codes confirmed
- ESD-Safe Packaging — Anti-static bag, foam cushioning, and humidity indicator card; outer carton labeled with inspection date, technician ID, and test results
Documentation Available Upon Request: Original Rockwell Automation datasheet, test report with channel-by-channel results, certificate of conformance, photos of physical unit pre-shipment, and customs/export documentation (HS Code 8537.10).
How to Source This Part
- Submit Your Inquiry — Add to cart or contact us at support@konmask.com with your required quantity, delivery timeline, and any documentation requirements. Response guaranteed within 24 hours on business days.
- Receive Quote & Inspection Report — We confirm stock availability, provide unit photos, test report, and a firm price. For orders ≥ 5 units, volume pricing applies automatically.
- Worldwide Fulfillment — Ships from our warehouse via DHL Express, FedEx International Priority, or UPS Worldwide. Typical transit: 3–7 business days to North America/Europe; 5–10 days to Southeast Asia, Middle East, and South America. Export documentation and customs clearance support included.
Application-Specific FAQ
Q: Can the 1746-IH16 accept signals from 2-wire (NAMUR-style) proximity sensors used in petrochemical applications?
A: Yes, with a caveat. Standard 2-wire NPN sensors typically source 1–3 mA in the OFF state (leakage) and 5–15 mA in the ON state. The 1746-IH16’s OFF-state leakage tolerance of ≤ 1.5 mA means some 2-wire sensors with higher leakage may cause false ON reads. For NAMUR sensors specifically (IEC 60947-5-6), an external NAMUR signal conditioner/repeater relay is recommended to convert the 1–2.1 mA / 3–20 mA NAMUR signal to a clean 24 VDC discrete output before connecting to the 1746-IH16.
Q: In automotive assembly line applications, can I mix sinking (NPN) and sourcing (PNP) sensors on the same SLC 500 rack?
A: Yes. Install the 1746-IH16 for your NPN/sinking sensor circuits and a 1746-IA16 (AC input) or 1746-IB16 (sourcing DC input) for PNP/sourcing circuits in adjacent slots. The SLC 500 backplane supports mixed I/O module types in any slot order. Ensure field commons are wired correctly — the 1746-IH16 requires the sensor’s negative (0 VDC) common connected to the module’s common terminal.
Q: For water treatment SCADA systems with 10–15 year lifecycle requirements, is the 1746-IH16 still being manufactured and supported by Rockwell Automation?
A: The SLC 500 platform is in Rockwell Automation’s End of Life phase, with the 1746-IH16 officially discontinued for new manufacture. However, Rockwell has committed to spare parts availability through authorized channels, and a robust certified surplus market ensures continued availability. For new installations with 15+ year lifecycle requirements, Rockwell recommends migrating to the Micro850 or CompactLogix 5380 platform. Konmask.com maintains stock of 1746-IH16 for existing system maintenance and can advise on migration paths — contact us for a lifecycle consultation.
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