1756-IA16I — ControlLogix 16-Point 120V AC Isolated Digital Input Module

The 1756-IA16I brings isolated channel architecture to the ControlLogix platform. Unlike standard grouped-common input modules, every one of the 16 input channels here has its own isolated common — meaning mixed voltage sources, different ground references, and high-noise field devices can all connect to the same module without interference between channels.

That isolation makes a real difference in industrial environments where sensors, limit switches, and relay contacts come from multiple circuits that don't share a common ground. Instead of designing separate I/O groups or adding external isolation relays, the module handles it at the hardware level.

Key Specifications

Parameter	Value
Part Number	1756-IA16I
Backplane	ControlLogix 1756
Input Points	16 (individually isolated)
Input Voltage	74–132V AC (nominal 120V AC)
Input Frequency	47–63 Hz
Input Current (at 120V AC)	10 mA (typical)
ON-State Voltage	74–132V AC
OFF-State Voltage	0–20V AC
Isolation (channel-to-channel)	250V AC continuous
Isolation (channel-to-backplane)	250V AC continuous
Filter Times (selectable)	1 ms, 2 ms, 9 ms (software configurable)
RTB Connector	1756-TBCH or 1756-TBS6H (36-pin)
Operating Temperature	0°C to 60°C
Current Draw (backplane, 5V)	250 mA
Current Draw (backplane, 24V)	2 mA

Application Scenarios

Power Distribution Panels In switchgear rooms where 120V AC control circuits come from multiple MCCs and transformer secondaries, the channel isolation prevents ground loop currents from corrupting input states. Each circuit connects to its own isolated channel without requiring a shared neutral.

Process Plant Field Instrumentation Pressure switches, flow switches, and level sensors in chemical or refining plants often operate from different 120V AC sources. The 1756-IA16I lets these devices connect to a single module without cross-circuit interference.

Legacy Machine Retrofits When replacing older relay-logic panels with modern PLC control, existing 120V AC wiring is often retained as-is. The isolated architecture avoids rewiring costs — devices from different original circuits connect directly.

High-Noise Environments Welding cells, large motor rooms, and arc furnace areas generate significant electrical noise. Channel isolation combined with the module's hardware filtering reduces false triggering without software workarounds.

FAQ

Q: What's the practical difference between isolated and non-isolated AC input modules?

Non-isolated modules group channels with a shared common — all channels in a group must connect to the same AC source phase and neutral reference. The 1756-IA16I gives each channel its own isolated common, so 16 devices from 16 completely different circuits can coexist on a single module. This eliminates ground loops and simplifies wiring in multi-source panels.

Q: Can the 1756-IA16I be used with 240V AC inputs?

No. The module is rated for 74–132V AC on-state input range. Applying 240V AC would exceed the input voltage rating and risk damaging the module. For 240V AC inputs, a different ControlLogix module with appropriate voltage specs is required.

Q: Does channel isolation affect scan time or diagnostics?

No. Isolated channels behave identically to standard inputs from the controller's perspective. Ladder logic, function block, and structured text programs address them the same way, and RSLogix/Studio 5000 diagnostics work normally.

Q: What removable terminal block is needed for this module?

The 1756-IA16I uses a 36-pin RTB. Compatible options include the 1756-TBCH (cage-clamp wiring) and the 1756-TBS6H (screw-clamp). The RTB is ordered separately from the module itself.

Q: How do I configure the input filter time?

Filter time is set in Studio 5000 (or RSLogix 5000) under the module's I/O configuration properties. Options are 1 ms, 2 ms, and 9 ms. Shorter filter times improve response speed; longer times improve noise rejection. Most applications run fine at the default 2 ms setting.

1756-IA16I New Sealed ControlLogix 16 Pt D/I 120V AC Module 1756IA16I