Description
Product Introduction & Engineering Value
When you need to command multiple proportional valves or drive speed references directly from an SLC 500 rack, channel density without signal degradation is everything. The Allen-Bradley 1746-NO4V delivers four high-accuracy voltage output channels in a single rack slot.
It bridges the gap between digital PLC logic and analog field devices, driving variable frequency drives and positioning dampers with minimal conversion latency. Engineers trust this module for seamless replacement in aging control cabinets, preventing costly retrofit redesigns.
Technical Specifications
- Output Channels: 4 voltage outputs
- Output Signal Ranges: ±10V DC, 0 to 10V DC, 0 to 5V DC, 1 to 5V DC
- D/A Converter Resolution: 14-bit (1.22 mV/LSB at ±10V)
- Output Update Time: < 1 ms for all 4 channels
- Backplane Current (5V DC): 55 mA
- Backplane Current (24V DC): 145 mA (when using backplane power)
- External Power Selection: Hardware Switch (SW1) for Backplane (BP) or External 24V DC (EXT)
- Isolation: 500V DC channel-to-backplane
- Operating Temperature: 0°C to 60°C (32°F to 140°F)
Field Application & The “Trench” Experience
A glass manufacturing facility lost control of its annealing lehr drive line when a 30-year-old analog card failed, locking three VFD speed commands at 0V. Swapping in a replacement 1746-NO4V restored multi-zone motor speed sync in under 15 minutes. The technician toggled power, set the hardware selector to backplane power, wired the removable terminal block, and re-engaged the process line smoothly.
- Dampers & Airflow Control: Outputting 0-10V signals to HVAC actuator drives in cleanroom environments.
- Web Tension Roller Positioning: Regulating pneumatic servo-regulator valves on high-speed paper slitting machines.
- Proportional Hydraulic Valves: Sending precise ±10V speed commands to hydraulic directional valves on injection molding equipment.
- 1746-NO4V
- 1746-NO4V
Transparency SOP: QA & Testing
- Connector & Board Inspection: Checking pin contacts, backplane edge connectors, and verifying output terminal block condition.
- Hardware Power Configuration Verification: Testing SW1 selector switch continuity between BP and EXT modes.
- Multi-Point Precision Calibration: Applying test logic in RSLogix 500 to send full-scale decimal values (e.g., -32,768 to +32,764) and measuring true voltage output via calibrated fluke meters.
- Load & Thermal Testing: Running active ±10V loop cycles across all 4 channels simultaneously under high-temperature burn-in conditions.
The Veteran’s Tech Trap Guide
- ⚠️ Power Selector Switch (SW1): The 1746-NO4V features a slide switch (SW1) on the side of the printed circuit board. If configured to “EXT” without an external 24V DC power supply wired to the terminal block, your analog outputs will stay dead at 0V regardless of what RSLogix reports.
- PRO TIP: 24V Power Supply Regulation: If you opt for an external power supply to reduce backplane current, do not attempt to share power from an SLC 1746-P1 or P2 auxiliary power loop. Standard 1746 power supply 24V DC auxiliary outputs do not meet the strict voltage regulation limits required by the NO4V analog circuitry.
- ⚠️ Data Justification Mismatch: Output values write to a 16-bit word format. Ensure your ladder logic math accounts for bit scaling; otherwise, writing unformatted integer values will result in scaled voltage command errors at the output pins.
Dynamic FAQ
Q: What is the difference between the 1746- and 1746-NO4I?
A: The 1746- outputs voltage signals (0-10V, ±10V DC), whereas the 1746-NO4I outputs current signals (4-20 mA, 0-20 mA).
Q: Can I replace a 1746- without rewiring the field terminal block?
A: Yes, the module uses a Removable Terminal Block (RTB). You can snap the RTB off the failed module and insert it directly into the replacement card without disconnecting individual control wires.
Q: Can I select different output voltage ranges per channel?
A: Output scaling is determined by the data written to the module’s output file registers in ladder logic. The module inherently supports ±10V DC, 0-10V DC, 0-5V DC, and 1-5V DC depending on data bit configuration.
Q: Are these units tested under live load conditions prior to shipment?
A: Yes, all units undergo rigorous bench testing on live SLC 500 backplanes using precision digital multimeters across all four channels.
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