Allen-Bradley 1794-ID2 FLEX I/O Incremental Encoder Module

The Allen-Bradley 1794-ID2 is a 2-channel incremental encoder module belonging to the FLEX I/O distributed automation series. It interfaces quadrature encoders and high-speed pulse transmitters directly with ControlLogix, CompactLogix, or PLC-5 controllers over a FLEX I/O backplane network. The module provides high-speed pulse processing, positioning measurement, and frequency tracking capabilities with independent differential and single-ended signal evaluation.

Quadrature Signal Processing and Inputs

The 1794-ID2 module features two independent counting channels, each containing four optocoupled input points. Channels support complementary (+ve and -ve differential) and non-complementary pulse signals for A, B, Z (marker/index), and Gate control functions. The module evaluates 1 or 2 pulse trains and processes input signal frequencies up to 100 kHz.

Backplane Integration and Mechanical Installation

Designed for DIN rail or panel mounting, the module attaches to a standard FLEX I/O terminal base unit, such as the 1794-TB2, 1794-TB3, or 1794-TB3G. Field signal connections are made at the terminal base, allowing removal and insertion under system power (RIUP) without disrupting field wiring. Module status and channel activity are indicated by 13 diagnostic LEDs located on the front panel.

Technical Specifications

Installation Requirements

Mount the 1794-ID2 module onto an approved 1794 terminal base unit prior to applying system logic power. Turn off field-side supply power during insertion or removal to prevent electric arcing. Ensure proper grounding practices on signal shield lines to prevent high-frequency noise interference on encoder pulse channels.

Frequently Asked Questions

Q: What terminal bases are compatible with the Allen-Bradley 1794-ID2 module?A: The 1794-ID2 module is compatible with 3-wire and 4-wire FLEX I/O terminal base units, including models 1794-TB2, 1794-TB3, 1794-TB3G, 1794-TBN, and 1794-TBNF.

Q: Can the 1794-ID2 accept single-ended signal inputs? A: Yes, each counter channel can be wired to evaluate non-complementary single-ended signals as well as complementary differential pulse streams.