Allen-Bradley 1746-FIO4V Analog Combination Module – 2 In, 2 Out, SLC 500

Technical Specifications

Main Features and Advantages

Two inputs and two outputs in one SLC 500 slot:​ The principal advantage of the 1746-FIO4V​ is density. A small SLC 500 chassis has limited backplane real estate, and dedicating two full slots to a handful of analogue points is expensive in both hardware and panel space. By combining two 15-bit voltage inputs and two 12-bit voltage outputs, the module provides a complete analogue interface in a single slot, leaving room for the digital I/O and communication modules the application also needs.Separate commons with isolation between the groups:​ The input side and output side of the 1746-FIO4V​ each have their own common terminal, and the two groups are isolated from one another. In a voltage-I/O application this matters: an output driving a load with a poor ground reference will induce noise on a shared common, and that noise will appear as jitter on the input readings. Keeping the groups separate and isolated is the correct hardware answer, and it removes a fault mode that would otherwise be diagnosed as a bad sensor or a failing input.Fifteen-bit inputs give usable precision at 0–10 V:​ The two inputs resolve the 0–10 V span at 15-bit, which is enough granularity for pressure, level, temperature, and position signals without requiring scaling tricks in the SLC 500 program. Combined with the 6 ms conversion time, the inputs are fast enough for control loops rather than merely for slow monitoring, and they integrate directly with the SLC 500’s analogue instruction set.Twelve-bit ±10 V outputs suit standard analogue loads:​ The two outputs cover the full ±10 V span at 12-bit resolution, which matches the reference input range of most variable-frequency drives, proportional valves, and analogue panel instruments. The symmetrical span also accommodates applications that need to command in both directions — forward and reverse, open and close, raise and lower — without biasing the signal in the program.A spare that drops in without re-engineering:​ Because the 1746-FIO4V​ is configured through the SLC 500 programming software as part of the slot definition, a verified spare can replace a failed unit and resume operation as soon as the processor sees the rack. Keeping the program file and the I/O configuration archived is what makes this true, and it is the single most valuable maintenance practice for an obsolete module: the hardware is simple; the risk is in losing the configuration.