Description
Hard-Numbers: Technical Specifications
- Output Channels: 8 single-ended (1-8 selectable via software configuration)
- Current Range: 0-20 mA or 4-20 mA (per-channel configurable)
- Voltage Range: 0 to +10V (unipolar) or -10V to +10V (bipolar)
- Resolution: 15-bit (unipolar modes); 16-bit (bipolar voltage mode)
- Update Rate: 8 milliseconds (all eight channels)
- Accuracy (Current Mode): ±0.1% of full scale at 25°C (typical); ±0.25% maximum
- Accuracy (Voltage Mode): ±0.25% of full scale at 25°C (typical); ±0.5% maximum
- Maximum Load (Current Mode): 0-850Ω at 20V supply; up to 1350Ω at 30V supply
- Maximum Load (Voltage Mode): 5 mA (minimum 2 kΩ resistance)
- Compliance Voltage: VUSER – 3V minimum to VUSER maximum (dependent on external supply)
- Isolation Rating: 250VAC continuous; 1500VAC for 1 minute (field-to-backplane, optical)
- Internal Power Draw: 110 mA from +5VDC backplane; 315 mA from external +24VDC
- External Power Required: 20-30 VDC isolated (mandatory), 10% max ripple
- Operating Temperature: 0°C to +60°C (+32°F to +140°F)
- Weight: 0.69 lbs (0.31 kg)
GE IC694ALG392
The Real-World Problem It Solves
You need eight analog outputs in one rack slot—control valves, VFD references, retransmission signals—and you don’t want to burn slots on multiple 2-channel cards. This module packs eight individually-configurable outputs into a single slot. Each channel can be current or voltage, unipolar or bipolar, all set in software. No jumpers to lose, no dip switches to misread at 2 AM.
Where you’ll typically find it:
- Process skids driving multiple control valves from a compact PLC
- Batch processing systems with 4-5 analog loops plus spare capacity
- Turbine control applications (IC694ALG392-CD variant for Mark I/II systems)
- Re-transmission of process variables to DCS inputs or chart recorders
Bottom line: Eight flexible analog outputs in one slot with built-in broken-wire detection on current loops.
Hardware Architecture & Under-the-Hood Logic
This module has no onboard microprocessor. It’s a pure DAC (digital-to-analog converter) array controlled by the CPU through the backplane. The PLC writes 16-bit values to %AQ registers, the module converts and drives the outputs. Per-channel configuration lives in the CPU’s hardware setup—not on the module.
Signal processing flow:
- CPU writes commanded values to %AQ reference addresses (one word per channel).
- Module receives digital values via backplane bus every I/O scan.
- Configuration data (range selection per channel) is read from CPU memory.
- Individual DACs convert digital values to analog voltage references.
- Output driver stages produce current or voltage based on per-channel configuration.
- External +24VDC powers the output drivers through an isolated supply domain.
- In current mode, open-wire detection monitors loop continuity and reports faults.
No channel-to-channel isolation. All eight outputs share a common isolated power domain. If you need per-channel isolation, move up to IC695ALG808 (8 isolated channels).
GE IC694ALG392
Field Service Pitfalls: What Rookies Get Wrong
External 24VDC Is Not Optional
The spec sheet says “user supplied 24VDC.” That’s not a suggestion—it’s a hard requirement. Without external power, the output drivers don’t function. Module OK LED might light (backplane 5V is present), but you’ll get zero output current. Connect external +24VDC via TB1 on the backplane left side or land it directly on the module terminal block.
Field Rule: Before commissioning, verify +24VDC with a meter at the module’s USER SUPPLY terminals. No voltage, no output—period.
Broken Wire Detection Only Works in Current Mode
The module reports open-wire faults for channels configured for current output. Voltage channels don’t get this diagnostic. The fault bits show up in the %I status word (bits 9-16 for channels 1-8). But here’s the catch: you have to configure the module to use 16 bits of status data, not 8. If you only configure 8 status bits, you’ll see module-level faults but not per-channel broken wire flags.
Quick Fix: In Proficy Machine Edition, set the %I reference length to 16 to get channel-level broken wire diagnostics. Configure 8 if you only need module OK and power supply OK bits.
Load Resistance Affects Temperature Derating
Current output load isn’t just about compliance voltage. The module dissipates heat proportional to load resistance. Lower resistance = more current = more heat. At 800Ω and below, accuracy degrades with temperature. The derating curves in the manual exist for a reason.
Field Rule: For 4-20mA loops, design for 250-500Ω loads when possible. Most valve positioners are 250Ω. Don’t push 850Ω loads in hot cabinets unless you’ve got good airflow.
Mixed Current/Voltage Modes Share a Common
All eight outputs reference a common terminal. If you’re mixing current loops with voltage outputs, you can create ground loops that inject noise. The module doesn’t isolate channels from each other—only from the backplane.
Field Rule: If mixing current and voltage outputs on the same module, keep voltage channel commons tied to the same ground reference as the current return. Don’t use multiple ground points in the field wiring.
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.
