Description
The 1756-IF16H is a high-density, 16-channel analog input module for the ControlLogix platform that supports HART (Highway Addressable Remote Transducer) protocol. It allows for the simultaneous acquisition of standard 4–20 mA analog signals and the digital HART data embedded on the same wire, enabling advanced device diagnostics and asset management without requiring additional hardware.
Availability and Procurement
- Condition: New Original (Factory Sealed) or New Surplus
- Warranty: 12-month standard industrial warranty
- Lead Time: Usually ships within 1–2 business days from stock
- Pricing: Subject to market conditions; contact our technical team for a firm, dated quote.
Technical Specifications
The 1756-IF16H is designed for high-performance process control applications where deep visibility into field instrumentation is required.
| Parameter | Specification |
| Number of Inputs | 16 Single-ended, 8 Differential, or 4 Differential (High-speed) |
| Input Range | 0 to 20 mA or 4 to 20 mA |
| Resolution | 16 bits |
| HART Support | Version 5, 6, and 7 (Point-to-point only) |
| Backplane Current (5.1 V) | 250 mA |
| Backplane Current (24 V) | 125 mA |
| Power Dissipation | 4.8 W (Maximum) |
| Module Keying | Electronic (Software-defined) |
| Removable Terminal Block (RTB) | 1756-TBCH or 1756-TBSH (Sold separately) |
Core Functionality and HART Integration
1. Integrated Asset Management
The primary advantage of the -IF16H is the ability to pass HART data directly to FactoryTalk AssetCentre or FDT/DTM software. This allows engineers to monitor device health, secondary variables (like internal temperature), and calibration dates without sending a technician into the field with a handheld communicator.
2. Digital Data Mapping
In the Logix Designer (RSLogix 5000/Studio 5000) I/O tree, the module presents additional tags beyond the raw analog value. You can map up to four secondary HART variables (PV, SV, TV, QV) per channel directly into your controller tags for use in your control logic.
3. Real-Time Diagnostics
The module can detect and report HART-specific faults, such as “Device Malfunction,” “Configuration Changed,” or “Analog Output Fixed,” providing a layer of diagnostic coverage that standard analog modules (-IF16) cannot match.
Engineering Insights: Deployment and Best Practices
As an architect who has integrated hundreds of these modules into refinery and chemical plant DCS systems, I recommend focusing on these areas:
1. Wiring and Interference
HART signals are low-frequency AC signals (1200/2200 Hz) superimposed on the DC loop.
- Constraint: Use high-quality twisted, shielded pair cabling. If the cable capacitance is too high (due to excessive length or poor cable choice), the HART digital signal will attenuate, leading to “HART Communication Failure” alarms in the module.
2. Powering the Loop
The 1756-IF16H is a non-isolated module.
- Warning: Most 16-channel configurations require an external 24 V DC power supply to power the field transmitters. Ensure your grounding strategy is consistent; floating loops can cause common-mode noise issues that disrupt both the 4–20 mA reading and the HART data.
3. Update Rates and RPI
The HART data is significantly slower than the analog signal.
- Real-world check: While the analog value updates at your Requested Packet Interval (RPI), the HART variables may take 1–2 seconds to refresh per channel depending on the number of active HART channels. Do not use HART variables for high-speed interlocking or safety-critical trips.
4. Filter Settings
The module features configurable notch filters (50 Hz, 60 Hz, 250 Hz, 500 Hz). In North America, setting this to 60 Hz is essential to reject induced mains noise. Choosing a lower filter frequency increases signal stability but increases the module’s conversion time.
FAQ
Q: Can I use the 1756-IF16H with standard 4–20 mA transmitters that don’t have HART?
A: Yes. The module functions perfectly as a standard analog input card. You can simply disable the HART feature in the software configuration for those specific channels.
Q: Is the 1756-IF16H a “hot-swap” module?
A: Yes, it supports RIUP (Removal and Insertion Under Power). You can replace the module without powering down the ControlLogix chassis, provided the field wiring is handled via the RTB.
Q: What is the difference between the 1756-IF16H and 1756-IF16?
A: The “H” denotes HART capability. Physically they are similar, but the IF16H contains the additional modem hardware required to modulate and demodulate the digital HART signal.
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