The IC694MDL230 is the individually isolated 120 VAC input module for Emerson's RX3i platform — 8 points, each with its own common terminal and each galvanically isolated from every other point to 1500 V RMS. This is a fundamentally different isolation architecture from the group-isolated modules common in most PLC I/O families. In a group-isolated module, 8 or 16 inputs share a common return — clean and simple when all the field devices are in the same panel, powered from the same control transformer. In the IC694MDL230, each of the 8 inputs is an independent floating channel: input 1 can monitor a limit switch on Machine A powered by Control Transformer A, input 2 can monitor a float switch on a water tank 200 meters away powered by a separate circuit, and input 8 can monitor an auxiliary contact in a motor starter bucket powered from a completely different panel — all without ground loops, without common-mode noise coupling, and without the risk of a single ground fault taking down all 8 channels.

The reactive input circuit: why no DC

The IC694MDL230 uses a reactive (resistor/capacitor) input circuit rather than a simple resistive divider. The capacitor limits the input current to approximately 12–14.5 mA at 120 VAC 60 Hz while dissipating virtually no real power — unlike a resistive input, which would dissipate roughly 1.7 W per channel at 120 VAC (14 mA × 120 V), or 13.6 W for 8 channels. The reactive design keeps the module's internal heat generation low enough that 8 channels can operate continuously at 60 °C ambient without derating. The trade-off is that the module is AC-only — the capacitor blocks DC current, so a 120 VDC signal will not register as an ON state. For applications with mixed AC and DC control circuits, the IC694MDL632 (125 VDC, product 7096 in this batch) and IC694MDL230 (120 VAC) are complementary — each optimized for the physics of its signal type.