Configured for differential current signal acquisition in the ControlLogix system, the Allen-Bradley 1756-IF16H (1756-IF16H Analog Input Module) provides 16 current input channels with HART communication capability. Each channel has a dedicated HART modem. The module accepts 0-20 mA and 4-20 mA signals.

Model and Ordering Reference

The current Rockwell Automation product page identifies 1756-IF16H as a ControlLogix 16 Point A/I HART module and specifies 0-20 mA and 4-20 mA input signals with no isolation between individual single-ended channels. The supplied country-of-origin information states USA, while the current manufacturer page lists Mexico; the manufacturer data should take precedence for procurement documentation.

Analog Input and HART Interface

The module provides 16 differential current inputs for 0-20 mA and 4-20 mA signals. A dedicated HART modem is provided for each channel, allowing HART device communication in addition to analog current acquisition.

The input resolution is specified as 16-21 bits. The input impedance is 249 ohm, and maximum input overvoltage protection is specified at 8 VDC. Open-circuit detection produces a positive full-scale reading within 5 s.

For signal wiring, the HART analog input manual provides separate terminal assignments for 2-wire and 4-wire HART devices. When a common supply is used, the manual specifies tying the IN- connection to RTN.

ControlLogix Electrical Characteristics

The module consumes backplane current from both the 5.1 VDC and 24 VDC supplies. The specified current draw is 200 mA at 5.1 VDC and 125 mA at 24 VDC, with total backplane power of 4.02 W. Maximum module power dissipation is 6 W.

Input channels have basic insulation from the backplane with a continuous isolation voltage rating of 50 V. Individual input channels are not isolated from one another. The isolation system was type tested at 1500 VDC for 60 s.

The module occupies one ControlLogix chassis slot. Electronic module keying is software configurable, while removable terminal block keying is user-defined mechanically. Compatible removable terminal blocks include 1756-TBCH and 1756-TBS6H.

Signal Integrity and HART Data Handling

Normal-mode noise rejection is specified as 74 dB at 50/60 Hz with the 15 Hz filter and 90 dB at 60 Hz with the 20 Hz filter. Common-mode noise rejection exceeds 90 dB at 50/60 Hz when the 15 Hz or 20 Hz filters are used.

Repeatability is better than 0.01% of range for the 15 Hz and 20 Hz filters. Calibrated accuracy is better than 0.13% of range across the specified filters. The typical calibration interval is 12 months.

The minimum analog module input scan time is filter dependent and ranges from 11 to 328 ms. The typical HART scan time is approximately 1 s when all channels are HART enabled. Pass-through messages, handheld communications, secondary masters, communication errors, and configuration changes can increase the HART update time.

Ordering Information

• 1 x Allen-Bradley 1756-IF16H ControlLogix 16 Point Analog Input HART Module
• 1 x Module housing and electronics assembly
• Removable terminal blocks are not inherently included with the I/O module and must be selected separately when required.
• Compatible RTB options include 1756-TBCH and 1756-TBS6H.

Field Installation Guidelines

Chassis installation

• Install the module in a compatible ControlLogix chassis position.
• Verify the available backplane power before installing the module.
• Use the configured electronic keying setting to prevent unintended module substitution.
• Provide sufficient cabinet clearance for thermal dissipation.

Signal wiring

• Use shielded copper conductors for analog signal wiring where specified.
• Route analog signal conductors separately from high-energy switching and power conductors.
• Follow the specified conductor category and system-level wiring requirements.
• Verify polarity at every IN+ and IN- terminal before energizing the loop.
• For common-supply HART wiring, follow the manufacturer wiring arrangement for the IN- and RTN connections.

Grounding and shielding

• Terminate cable shields according to the plant grounding design and applicable ControlLogix wiring guidelines.
• Avoid creating unintended ground loops through multiple shield termination points.
• Do not assume that individual input channels are galvanically isolated; the 1756-IF16H provides no isolation between individual input channels.

Environmental limits

• Maintain an operating ambient temperature within 0 to 60 deg C.
• Keep relative humidity within the specified non-condensing range.
• The module uses an open-style enclosure and therefore requires installation inside an appropriate equipment enclosure.

Frequently Asked Questions

• Does the 1756-IF16H support HART?
  Yes. It provides a dedicated HART modem for each of its 16 differential current input channels.
• What analog signals does the module accept?
  The supported input ranges are 0-20 mA and 4-20 mA differential current signals.
• Are the 16 input channels individually isolated?
  No. The module provides no isolation between individual input channels. Isolation is specified between input channels and the backplane.
• How much backplane current does the module require?
  The specified backplane current is 200 mA at 5.1 VDC and 125 mA at 24 VDC, with 4.02 W total backplane power.
• What is the module scan time?
  Analog input scan time is filter dependent and specified from 11 to 328 ms. Typical HART scanning is approximately 1 s with all channels enabled.
• What terminal blocks are compatible?
  The specified removable terminal block options are 1756-TBCH and 1756-TBS6H. RTBs must be ordered separately when required.
• What is the operating temperature range?
  The specified operating ambient range is 0 to 60 deg C. Nonoperating storage temperature is specified from -40 to +85 deg C.
• Can the module be used for individually isolated signal loops?
  No. Individual input channels are not isolated from one another. Applications requiring channel-to-channel isolation require an appropriate isolated analog input module.