FOXBORO P0926MX Replacement Solution for I/A Series

Product Overview

FOXBORO P0926MX Replacement Solution for I/A Series: Seamless Transition from Legacy Signal Isolation

The FOXBORO P0926MX is a dual-output signal splitter and galvanic isolator engineered for the Foxboro I/A Series Distributed Control System (DCS). As aging I/A Series installations approach end-of-life or face component obsolescence, plant engineers and procurement teams increasingly require a reliable, drop-in replacement that preserves loop integrity, maintains 4-20 mA signal fidelity, and avoids costly process shutdowns. TOPNLMS supplies the P0926MX as a tested, ready-to-ship unit backed by a 12-month warranty, enabling a smooth migration path from legacy field instrumentation to modernized control architectures.

The P0926MX accepts a single 4-20 mA input from a field transmitter and delivers two fully isolated, galvanically separated 4-20 mA output signals to the I/A Series FBM (Field Bus Module) or to a secondary recorder, safety system, or historian. This dual-output topology is critical in retrofit projects where the original single-loop wiring must simultaneously feed both the legacy DCS and a new supervisory layer — such as a Yokogawa CENTUM VP historian or an ABB 800xA OPC gateway — without introducing ground loops or common-mode interference.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful I/A Series signal isolation upgrade rarely involves a single component. In practice, the P0926MX replacement is part of a broader marshalling cabinet and field loop modernization effort. When migrating from an older Foxboro I/A Series installation, engineers typically address the FBM input cards simultaneously — modules such as the Foxboro FBM201 or FBM202 analog input field bus modules are common companions to the P0926MX in the same marshalling cabinet, and their terminal assignments must be verified against the new isolator’s output wiring before commissioning.

On the power distribution side, the 24 V DC auxiliary power rail feeding the P0926MX is often shared with other DIN-rail-mounted devices in the same cabinet section. Replacing or auditing the Foxboro P0914XS or equivalent 24 V DC power supply module at the same time prevents nuisance trips caused by marginal rail voltage during the transition period. If the plant is also upgrading its HART device management infrastructure, the P0926MX’s HART pass-through capability allows the existing Foxboro HART multiplexer — such as the P0922VW HART interface module — to continue polling field transmitters without rewiring.

For projects that extend beyond signal isolation into full loop modernization, the P0926MX is frequently installed alongside Foxboro I/A Series FBM207 or FBM237 HART-enabled analog input modules, which replace older non-HART FBMs and allow the DCS to access HART device diagnostics natively. In marshalling cabinets where space is constrained, the slim DIN-rail profile of the P0926MX pairs well with Foxboro P0916SA terminal blocks and P0917TA jumper assemblies, preserving the existing cable tray and conduit routing without modification.

When the migration scope includes the control room side, the P0926MX’s dual outputs support simultaneous connection to both the legacy I/A Series Workstation (IWS) historian and a new Foxboro Evo DCS node or a third-party SCADA system — eliminating the need for a temporary signal splitter during the cutover window. This architecture is particularly valuable in continuous process industries such as refining, petrochemicals, and power generation, where even a 30-minute unplanned outage carries significant financial and safety consequences.

For sites performing a phased migration from the I/A Series to a modern platform, the P0926MX also integrates cleanly with Pepperl+Fuchs or MTL signal conditioning barriers already present in the hazardous-area zener barrier panels, maintaining IS (intrinsic safety) loop compliance without requiring a full barrier replacement. Procurement teams should note that the P0926MX is available from TOPNLMS as a single unit or in multi-unit lots, with pre-shipment functional testing, calibration verification, and full documentation package included.

Retrofit Guidance FAQ

Q: Can the P0926MX be wired directly into the existing I/A Series marshalling cabinet without modifying the terminal block layout?
A: Yes. The P0926MX uses a standard 6 mm DIN-rail footprint and screw terminals compatible with 2.5 mm² conductors. In most I/A Series marshalling cabinets, the existing terminal block rows and cable tray routing can be retained. Verify the input terminal polarity (+ / −) against the field transmitter loop wiring before energizing.

Q: Does the P0926MX support HART communication pass-through?
A: Yes. The P0926MX passes the HART FSK signal superimposed on the 4-20 mA loop, allowing HART-capable FBMs or a HART multiplexer to communicate with field devices without additional wiring. Confirm that the load impedance on the HART master side meets the minimum 230 Ω requirement.

Q: Is any PLC or DCS re-programming required after replacing the legacy isolator with the P0926MX?
A: No re-programming is required for a like-for-like signal replacement. The P0926MX outputs the same 4-20 mA signal range as the predecessor module. If the second output channel is newly utilized (e.g., to feed a historian or safety system), the receiving device’s analog input channel must be configured, but the I/A Series FBM configuration itself does not change.

Q: What is the physical installation space requirement?
A: The P0926MX occupies a standard 6 mm DIN-rail slot. No additional cabinet space is required compared to the legacy single-output isolator it replaces. If replacing a wider legacy module, the freed DIN-rail space can be used for additional terminal blocks or cable management accessories.

Q: How is the 24 V DC power supply connected?
A: The P0926MX requires an external 24 V DC supply connected to the dedicated power terminals (not loop-powered). The supply must be capable of sourcing the combined current draw of all isolators on the shared rail. A dedicated 24 V DC power supply module with adequate current rating is recommended for new installations.

Q: What commissioning steps are required after installation?
A: After physical installation and wiring, apply 24 V DC power and inject a known 4-20 mA test signal at the input. Verify both output channels read the expected value at the FBM analog input card and at the secondary receiving device. Perform a full-range linearity check (4 mA, 12 mA, 20 mA) and document results before returning the loop to service.

Warranty Assurance

Every FOXBORO P0926MX unit supplied by TOPNLMS is covered by a 12-month warranty from the date of shipment. Prior to dispatch, each unit undergoes a pre-shipment functional test that verifies input-to-output signal accuracy across the full 4-20 mA range, galvanic isolation integrity between channels, and power supply terminal continuity. A calibration verification record is available upon request.

In the event of a confirmed unit defect within the warranty period, TOPNLMS will arrange a replacement shipment or issue a credit note, subject to return of the defective unit for inspection. Our after-sales response target is one business day for initial fault assessment and three business days for replacement dispatch from our Xiamen warehouse.

For procurement teams managing planned maintenance shutdowns or emergency replacements, TOPNLMS maintains buffer stock of the P0926MX and can confirm availability, lead time, and export documentation (commercial invoice, packing list, certificate of origin) at the time of inquiry. Expedited air freight options are available for urgent requirements.

For volume orders, framework agreements, or technical pre-sales support, contact our engineering sales team directly.