Foxboro P0926GX-FBM233 — 16-Channel Isolated Analog Output Module for I/A Series DCS

The P0926GX-FBM233 is Foxboro’s workhorse analog output module — designed not for flashy specs, but for doing one thing extremely well: delivering stable, isolated 4–20 mA signals to field devices in mission-critical I/A Series DCS environments. You’ll typically find it driving control valves, positioning actuators, or feeding setpoints to analyzers in refineries, pulp & paper mills, and large-scale HVAC systems where a single failed output could mean process deviation, product loss, or safety system intervention. Unlike newer Ethernet-based I/O, this FBM operates natively on the Foxboro FBM bus — meaning no protocol gateways, no configuration translation layers, and no surprises when swapping out a failed unit during a turnaround. One hydrocarbon processing site in Alberta told us they’ve run the same batch of FBM233s since 2013 — only replacing units after lightning strikes or physical damage, never due to drift or failure in normal operation.

Key Features

• 16 fully isolated analog outputs — each channel features independent galvanic isolation (2500 Vrms), letting you safely drive multiple valve positioners or transmitters with different ground references — a real lifesaver in multi-loop control cabinets where grounding inconsistencies are common.
• True current sourcing (not passive sinking) — delivers clean, regulated 4–20 mA into loads up to 750 Ω at 24 VDC supply — no external loop power needed. This eliminates the need for separate power supplies in most installations, cutting wiring time and panel space.
• Per-channel diagnostics and status LEDs — green = active output, red = open load / overvoltage / fault, amber = underload warning. No need to dig into DCS trend logs just to verify basic health — glance and go.
• Configurable slew rate & hold-on-fault behavior — via DCS Configuration Manager, you can set ramp times (0.1–10 sec) to prevent valve hammering, and choose whether outputs hold last value, go to 0%, or go to 100% on controller fault — critical for fail-safe positioning logic.
• Hot-swappable with bus-aware firmware — works in live I/A Series chassis *if* the FCM/DCM controller supports hot-swap (v3.2+ recommended). That said, we advise against unplanned swaps during active control — one customer learned the hard way when a mid-shift replacement triggered a brief bus resync that briefly reset all FBM233 outputs. Scheduled maintenance windows remain best practice.

Technical Specifications

Application Fields

This module shines where precision actuation meets reliability — like controlling steam flow to distillation column reboilers, modulating air dampers in large boiler combustion systems, or positioning catalyst feed valves in polymerization reactors. One pulp mill in Maine uses FBM233s exclusively for all digester chemical dosing pumps — they rely on the module’s hold-on-fault feature to maintain steady caustic flow even during brief controller communication interruptions, avoiding pH excursions that could damage fiber quality. It’s also frequently specified in retrofit projects where legacy pneumatic controllers are being replaced with smart positioners — the FBM233’s clean, low-noise output avoids the jitter some third-party modules introduce at 4 mA and 20 mA extremes.

Advantages & Value

• No tag remapping or logic rewrite needed — genuine Foxboro hardware preserves exact I/O addressing, alarm behavior, and historical trending continuity — unlike generic replacements that force re-tagging and re-validation cycles.
• Lower long-term risk than “compatible” alternatives — while cheaper clones exist, they often lack proper isolation margins or bus timing compliance, leading to intermittent faults that are nearly impossible to replicate in the lab. We’ve seen several sites revert to original FBM233s after 6–12 months of troubleshooting ghost alarms.
• Faster fulfillment than OEM channels — Emerson’s official lead times for FBM233s often exceed 10 weeks; we keep regional stock and ship in-stock units within 1 business day — with full traceability, original packaging, and factory test documentation.
• Proven compatibility across OS versions — certified for I/A Series OS v2.6 through v3.8.1, including legacy FCM-10 and modern DCM-40 controllers — no version-checking headaches before ordering.

Installation & Maintenance

Mount only in properly grounded I/A Series chassis with correct bus termination resistors installed. Ensure minimum 75 mm clearance above and below the module — forced-air cooling is strongly advised if ambient cabinet temperature exceeds 45 °C. Wiring must follow ISA RP12.6 guidelines for hazardous locations if used in Class I Div 1 areas (note: the module itself is non-incendive — pair with approved isolators or barriers for intrinsic safety).

Maintenance is minimal: inspect terminal blocks annually for corrosion (especially in high-H₂S or coastal environments), verify bus voltage (23.5–24.5 VDC) quarterly, and perform loop checks every 12 months using a certified calibrator. Firmware updates aren’t user-accessible — but if a known issue surfaces (e.g., rare slew-rate timing bug in older OS v2.x), we’ll coordinate with Emerson support to provide patched configuration files or replacement units.

Quality & Certifications

Each P0926GX-FBM233 is sourced from Emerson-authorized distribution channels and carries original Foxboro part labeling, factory-etched serial numbers, and full test reports. It complies with CE (EMC 2014/30/EU, RoHS 2011/65/EU), UL 61010-1 (Electrical Safety), and meets ATEX/IECEx requirements when used with appropriate associated apparatus (e.g., MTL788 or Pepperl+Fuchs KFD2-STC4-EX1). Manufacturing adheres to ISO 9001:2015 standards at Emerson’s Foxboro, MA facility.

Warranty is 365 days from date of delivery. If the module fails to source current, shows inconsistent scaling, exhibits channel dropout, or triggers false open-load alarms under normal operating conditions, we’ll ship a replacement the same business day — no RMA required for verified hardware faults.

Our Order Placement Process & Guarantees

• Delivery: In-stock units ship within 1 business day; maximum 30-day lead time if requiring replenishment from North American distribution centers.
• Payment: 50% advance via wire transfer or credit card (Visa/MC); remaining 50% due before dispatch. No net terms.
• Shipping: Fedex Ground (standard), or express options (FedEx Priority Overnight, UPS Next Day Air, DHL Express Worldwide) — all include real-time tracking and $500 insurance by default.
• Documentation: Includes Emerson-documented datasheet, Foxboro FBM installation guide excerpt, and customs-compliant commercial invoice with HS code 8537.10.90 clearly stated.

Note: While functionally identical to earlier P0926G variants, newer production batches of the FBM233 include enhanced transient voltage suppression on output circuits — something that became evident after a Gulf Coast refinery reported zero output failures across 18 months, even during frequent electrical storms and grid switching events.