Description
Hard-Numbers: Technical Specifications
- Channels: 4 analog inputs (differential)
- Current Range: 4-20 mA (default) / 0-20 mA (jumper selected)
- Resolution: 12-bit (4 µA/count at 4-20mA; 5 µA/count at 0-20mA)
- Conversion Speed: 0.5 ms per channel
- Update Rate: 2 ms for all four channels
- Input Filter Response: 325 Hz
- Input Impedance: 250 ohms
- Common Mode Voltage: 200 V (survives with reduced performance)
- Isolation Rating: 250 VAC continuous; 1500 VAC for 1 minute (optical, field-to-backplane)
- Common Mode Rejection: >70 dB at DC and 60 Hz
- Cross-Channel Rejection: >80 dB (DC to 1 kHz)
- Absolute Accuracy: 0.1% full scale + 0.1% reading
- Power Draw: 25 mA @ +5VDC (backplane) + 100 mA @ +24VDC isolated
- Calibration: Factory calibrated (no field trim pots)
- Hot Swap: Not supported—power down before insertion/removal
GE IC694ALG221
The Real-World Problem It Solves
Same function as the base IC694ALG221—this is Revision A of the same hardware. If you’re replacing a failed card and your spare has the “A” suffix, it’s a direct swap. No configuration changes, no firmware updates, no surprises.
Where you’ll typically find it:
- Same applications as IC694ALG221: pressure transmitters, level loops, flow meters
- Replacement stock for systems that shipped with Revision A hardware
- Sites that standardized on Revision A during initial procurement
If you’re designing a new system, either revision works. If you’re maintaining an existing rack, match the revision you’re pulling out.
Hardware Architecture & Under-the-Hood Logic
Revision A carries the same internal architecture as the base model. No microprocessor on board—all signal processing happens at the CPU level. The “A” designation indicates a hardware revision, typically addressing component sourcing, PCB layout tweaks, or manufacturing process changes rather than functional differences.
- Current Loop Entry – 4-20mA signal enters through (+) terminal, passes through the internal 250Ω precision resistor, exits through (-) terminal. Voltage drop across this resistor is what the ADC reads.
- Range Selection via Jumpers – Two hardware jumpers on the terminal block: Jumper 1 for channels 1-2, Jumper 2 for channels 3-4. No jumper = 4-20mA (default). Jumper installed = 0-20mA.
- A/D Conversion and Multiplexing – 0.5 ms conversion per channel. Multiplexer cycles all four channels in 2 ms total. 12-bit ADC sends raw counts to CPU—scaling is done in your PLC logic, not in firmware.
Field Service Pitfalls: What Rookies Get Wrong
Assuming Revision A Means New FeaturesThe “A” suffix doesn’t add capability. It’s a hardware revision, not a feature upgrade. If you’re expecting better resolution, faster update rates, or new diagnostics, you’re looking at the wrong card.
- Field Rule: Treat IC694ALG221A as identical to IC694ALG221 for all configuration and wiring purposes. The revision letter only matters for inventory tracking and warranty documentation.
Mixing Revisions in the Same RackSome sites get nervous about mixing IC694ALG221 and IC694ALG221A in the same backplane. There’s no technical reason you can’t—they’re functionally identical. But if your maintenance procedures require revision matching, stick to your site rules.
- Quick Fix: If you’re swapping a failed card and only have a different revision in stock, check your site’s spare parts policy. Most sites allow direct substitution. If yours doesn’t, document the exception and move on.
Same Pitfalls as Base ModelAll the rookie mistakes from IC694ALG221 apply here: confusing jumper positions, wiring voltage signals to a current card, forgetting external loop power for two-wire transmitters. The revision letter doesn’t change any of that.
GE IC694ALG221
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
