Description
IC694ALG221 Product Overview
The IC694ALG221 is a four-channel, 12-bit analog current-input module that plugs into any I/O slot of an Emerson PACSystems RX3i rack. It is most often used to bring 4–20 mA or 0–20 mA process signals—pressure, flow, temperature, valve position, motor load—into the PLC without adding external shunts or signal conditioners.
The IC694ALG221 is a four-channel, 12-bit analog current-input module that plugs into any I/O slot of an Emerson PACSystems RX3i rack. It is most often used to bring 4–20 mA or 0–20 mA process signals—pressure, flow, temperature, valve position, motor load—into the PLC without adding external shunts or signal conditioners.
Within the automation architecture the card sits at the “sensor interface” layer: it presents a 250 Ω precision burden to the loop, digitizes the resulting 1–5 V drop to 12-bit resolution, and makes the raw or scaled value available to the RX3i CPU every 2 ms. Differential inputs and optical isolation (250 V working) reject ground-shift noise common in motor-drive or power-plant environments, while the <1 LSB accuracy specification keeps servo or flow-control loops stable.
Being part of the RX3i family means the module is hot-swappable, rack-powered, and automatically recognised by the CPU—no DIP-switch banks and no external 24 V supply needed when located in a remote or expansion backplane.
IC694ALG221
Technical Specifications
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Model Number: IC694ALG221
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Manufacturer: GE / Emerson
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Product Type: Analog Current Input Module
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Channels: 4 differential, isolated
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Input Ranges: 4–20 mA (default) or 0–20 mA (jumper-selectable per pair)
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Resolution: 12-bit (4 µA per count @ 4–20 mA; 5 µA per count @ 0–20 mA)
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Update Rate: 2 ms (all four channels)
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Input Impedance: 250 Ω ±0.1 %
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Isolation: 250 V working, optical
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Accuracy: ±0.1 % full scale + 0.1 % reading
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Power Consumption: 25 mA @ +5 VDC; 100 mA @ +24 VDC isolated
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Filter Response: 325 Hz (–3 dB)
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Hot Swap: Supported in RX3i universal backplane
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Temperature: –40 … +70 °C operational; –40 … +85 °C storage
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Agency Approvals: UL, CE, ATEX Zone 2, ABS, BV, DNV-GL, LR
Core Features & Customer Value
250 Ω burden resistor on-board – Eliminates external shunts and wiring errors; the resistor is factory-trimmed to ±0.1 %, so loop accuracy is maintained without user calibration.
250 Ω burden resistor on-board – Eliminates external shunts and wiring errors; the resistor is factory-trimmed to ±0.1 %, so loop accuracy is maintained without user calibration.
Differential & isolated inputs – 250 V optical isolation rejects ground-shift noise from VFDs or breaker operations, letting you run instrument cable in the same tray as 480 V power without data corruption.
2 ms update for all four channels – Fast enough for anti-surge, flow-control, or motor-current loops; you get deterministic data every scan without adding CPU overhead.
Jumper-selectable ranges – Move one jumper to switch a channel pair from 4–20 mA to 0–20 mA, so you can mix sensor types on the same card without ordering different part numbers.
Hot-swap capable – Module can be inserted or removed while the RX3i rack is powered, reducing downtime during loop calibration or sensor replacement.
IC694ALG221
Typical Applications
In combined-cycle plants the IC694ALG221 is routinely installed in the “analog input” section of RX3i racks that govern gas-turbine fuel flow, inlet-guide-vane position, and cooling-water temperature. The 2 ms update keeps the speed-control loop responsive, while the 4–20 mA range matches the plant’s standard temperature and pressure transmitters.
In combined-cycle plants the IC694ALG221 is routinely installed in the “analog input” section of RX3i racks that govern gas-turbine fuel flow, inlet-guide-vane position, and cooling-water temperature. The 2 ms update keeps the speed-control loop responsive, while the 4–20 mA range matches the plant’s standard temperature and pressure transmitters.
In pipeline compressor stations the same module reads 4–20 mA signals from suction/discharge pressure transmitters and anti-surge valve positioners, feeding real-time data to the anti-surge PID running in the RX3i CPU.
Because the card is certified for Zone 2 and marine environments, it is also used on off-shore platforms for well-head pressure and subsea valve-position feedback without needing additional isolation barriers.
