Allen-Bradley 1756-IF6CIS ControlLogix Analog Input Module

The Allen-Bradley 1756-IF6CIS, also cataloged as the 1756-IF6CIS Analog Input Module, operates as a dedicated hardware component for acquisition of 0…20 mA sourcing current loop signals within ControlLogix backplane I/O structures. The module provides 6 individually isolated input channels with sigma-delta conversion and fixed 16-bit resolution processing.

Hardware Specifications

ControlLogix Current Sourcing Loop Architecture

The module implements independent current sourcing per channel, where each input loop is electrically isolated and driven through internal sourcing circuitry. This configuration allows direct interface with passive field transmitters requiring excitation from the module side rather than external loop power supplies.

Sigma-delta conversion is used to sample low-level current variations across all six channels, with digital filtering applied prior to backplane data transfer. Each channel maintains a fixed 0.34 uA/bit quantization step within the 0…20 mA range.

Backplane loading is distributed across 5 VDC logic rail (250 mA) and 24 VDC field interface rail (275 mA), with total module dissipation limited to 5.1 W under maximum thermal condition.

Channel isolation prevents inter-loop current coupling during mixed load conditions, preserving measurement separation under multi-transmitter configurations.

Frequently Asked Questions

Q: Can all six channels operate simultaneously in sourcing mode?
A: Yes, all 6 channels operate independently with dedicated sourcing circuits and no shared current path.

Q: Does the module require external loop power supplies?
A: No external loop supply is required for passive devices; current sourcing is provided per channel by the module.

Q: What happens to resolution under high filtering settings?
A: Sigma-delta conversion resolution remains fixed at 16-bit, while effective update rate is reduced by digital filtering.

Field Installation Guidelines

The module must be installed into a ControlLogix chassis with proper backplane alignment to avoid connector stress. Terminal blocks (1756-TBCH / 1756-TBS6H) must be fully seated prior to energizing field loops.

Shielded current loop wiring is required for all 0…20 mA channels. Shields should be terminated at a single chassis ground reference to avoid loop-induced measurement drift.

Separation between sourcing loop wiring and high-voltage conductors must be maintained to preserve channel isolation integrity during operation.