Allen-Bradley 1746-NO4V Analog Output Module – SLC 500

Allen-Bradley 1746-NO4V: 4-Channel Voltage Analog Output Module for SLC 500 Control Architecture

The Allen-Bradley 1746-NO4V is a 4-channel voltage analog output module engineered for the SLC 500 modular I/O platform. Occupying a single slot in any 1746-series chassis, it converts 16-bit digital words written by the SLC processor into calibrated DC voltage signals — ±10 VDC or 0–10 VDC, software-selectable per channel — that drive field actuators including proportional control valves, variable-frequency drives, electro-pneumatic positioners, and analog setpoint inputs on third-party PID controllers. Its role in the control loop is deterministic: the SLC processor writes output image data during each scan cycle, the module latches the value, and the DAC circuit settles to the commanded voltage within the specified slew time, ensuring that downstream actuators receive a stable, repeatable reference independent of backplane bus loading from adjacent modules.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The 1746-NO4V is built around a 12-bit successive-approximation DAC architecture with per-channel output amplifiers. Each channel’s digital word is latched from the SLC output image table at the end of every processor scan, then converted by the DAC and buffered through a precision op-amp stage before reaching the terminal block. The op-amp output stage is configured as a voltage follower with gain-setting resistors that define the ±10 V or 0–10 V span, and the range selection is implemented via an analog multiplexer controlled by a configuration bit in the module’s output data file — no hardware jumpers are required, which eliminates the risk of field-wiring errors caused by jumper misplacement.

The galvanic isolation barrier between the field-side circuitry and the SLC backplane is implemented using transformer-coupled DC-DC conversion for the analog supply rails and optocoupler-based signal paths for the configuration and status data. This architecture provides a 1,500 VAC withstand rating, which is sufficient to suppress common-mode transients generated by large motor starters or capacitor bank switching events on the same panel bus. The isolation also prevents ground loops between the SLC chassis ground reference and the field instrument ground, a common source of signal drift in multi-panel installations.

EMC performance is addressed at the PCB level through a combination of ground plane partitioning — separating the digital, analog, and isolated field domains — and ferrite bead filtering on the backplane power rails. The output terminal traces are routed away from the digital clock lines to minimize capacitive coupling, and the module housing provides shielding continuity when seated in the chassis. These design choices allow the 1746-NO4V to maintain its ±0.5% full-scale accuracy specification in environments with conducted emissions up to the EN 61000-4-4 Level 3 criterion.

The short-circuit protection circuit on each output channel uses a current-sensing resistor in series with the output amplifier. When the sensed current exceeds the protection threshold — indicating a wiring fault or a load impedance below the 1 kΩ minimum — the amplifier is folded back to a safe operating point without latching. Once the fault is cleared, the output recovers to the commanded value within the next scan cycle without requiring a processor reset or module re-initialization. This self-recovering behavior is critical in continuous-process applications where a manual reset would require a process interruption.

System Integration Benefits

• Zero-overhead backplane communication: The 1746-NO4V maps directly into the SLC output image table as a standard 4-word block. No special ladder logic instructions or MSG instructions are required; the processor writes to O:x.0 through O:x.3 and the module handles the rest, keeping scan time impact negligible even in tight 10 ms cycle applications.
• Per-channel range flexibility without rewiring: Switching a channel between ±10 V and 0–10 V is accomplished by toggling a configuration bit in the output data file, allowing engineers to adapt to field device changes during commissioning or after a device swap without touching the terminal block wiring.
• Deterministic output update timing: Because the module latches output data synchronously with the SLC scan, the maximum latency between a processor write and a stable analog output is bounded by one scan cycle plus the DAC settling time (typically < 1 ms). This determinism is essential for closed-loop control applications where output jitter would introduce phase error into the control algorithm.
• Diagnostic transparency via output data file: The module reflects its operational status through bits in the output image, allowing the ladder program to detect open-wire conditions and short-circuit faults without external diagnostic hardware. Fault states can be mapped directly to HMI alarm tags in RSLogix 500.
• Backplane-only power architecture: The absence of an external 24 VDC supply requirement simplifies panel wiring, reduces terminal block count, and eliminates a potential single point of failure. The 120 mA draw at 5 VDC is well within the budget of all standard 1746-series power supplies.
• Chassis-agnostic slot placement: The 1746-NO4V can occupy any I/O slot in a 4-, 7-, 10-, or 13-slot chassis without slot-specific restrictions, giving system designers full flexibility in module arrangement for thermal management or cable routing optimization.
• Compatibility with RSLogix 500 offline configuration: The module’s I/O configuration can be defined and verified in an offline RSLogix 500 project before the hardware is physically installed, enabling parallel engineering workflows where software development and panel fabrication proceed simultaneously.
• Long-term parts availability through the industrial aftermarket: The SLC 500 platform has an extensive installed base accumulated over three decades of deployment. The 1746-NO4V remains available through authorized distributors and verified surplus channels, supporting maintenance programs for facilities that have standardized on the SLC 500 architecture and are not yet ready to migrate to ControlLogix or CompactLogix.

Quality Assurance & Global Logistics

Every Allen-Bradley 1746-NO4V unit offered through siemensplc.com is sourced from verified supply channels with full date-code and serial-number traceability. Prior to dispatch, each module undergoes a functional verification procedure that confirms DAC output accuracy across all four channels at both the ±10 V and 0–10 V ranges, backplane communication integrity, and isolation resistance above the rated threshold. Units that do not meet the original Rockwell Automation factory acceptance criteria are rejected and not offered for sale.

Shipments originate from our warehouse in Xiamen, China — a major logistics hub with direct access to international freight forwarding services via Xiamen Gaoqi International Airport and the Port of Xiamen. Standard export packaging uses anti-static foam inserts and moisture-barrier bags to protect the module’s PCB and connector contacts during transit. For time-critical requirements, DHL Express and FedEx International Priority services are available with typical transit times of 3–5 business days to most destinations in Europe, North America, Southeast Asia, and the Middle East. All shipments include a commercial invoice, packing list, and certificate of conformance. Export classification is reviewed for each destination country to ensure full compliance with applicable trade regulations.

A 12-month warranty covers all units against defects in materials and workmanship from the date of shipment. Warranty claims are processed with a target response time of 24 hours, and replacement units are dispatched from stock where available to minimize customer downtime. Technical support for installation, RSLogix 500 configuration, and system integration questions is provided by our engineering team at no additional charge.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.