Pepperl+Fuchs KFD2 Modules: KFD2-STC4-EX1.H

Technical Dossier

Product Details And Specifications

Pepperl+Fuchs KFD2 Series: Comprehensive Module Range and Technical Overview

The Pepperl+Fuchs KFD2 series represents one of the most widely deployed families of DIN-rail-mounted signal conditioners and isolating barriers in global heavy industry. Installed across chemical processing plants, nuclear power facilities, oil refineries, and offshore platforms, KFD2 modules serve as the critical interface layer between hazardous-area field instruments (4–20 mA transmitters, thermocouples, RTDs, discrete I/O) and safe-area control systems including DCS, PLC, and SCADA architectures. The series is engineered to ATEX, IECEx, and FM/CSA standards, enabling intrinsically safe (Ex ia) and non-incendive circuit topologies in Zone 0/1/2 and Division 1/2 classified areas. The KFD2 platform has accumulated decades of installed base in facilities operated by BASF, Shell, ExxonMobil, Sinopec, and comparable tier-1 industrial operators, making long-term spare parts availability a critical procurement concern.

The Evolution of KFD2 Architecture

The KFD2 series was introduced by Pepperl+Fuchs as a successor to earlier KFD and KFA barrier families, consolidating signal conditioning, galvanic isolation, and hazardous-area protection into a single compact 20 mm or 40 mm DIN-rail module. Early KFD2 variants relied on transformer-based galvanic isolation with passive loop power. Subsequent generations introduced active signal processing, HART transparency (allowing HART pass-through for field device diagnostics without breaking the 4–20 mA loop), and enhanced EMC shielding compliant with EN 61326. The KFD2-STC4 sub-family specifically addresses 2-wire transmitter power supply with current output, a topology dominant in legacy DCS installations using FOUNDATION Fieldbus-adjacent wiring infrastructure. As facilities transitioned from pneumatic to electronic instrumentation through the 1990s and 2000s, KFD2 modules were retrofitted into existing marshalling cabinets, creating a long-tail installed base that persists through the 2020s. Pepperl+Fuchs has progressively migrated new designs toward the KFD3 and FieldConnex series, placing the KFD2 family in a mature/end-of-active-development lifecycle. However, the series remains in production for the majority of catalog numbers, with select models transitioning to managed availability status.

KFD2 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked models within the Pepperl+Fuchs KFD2 series, organized by functional category. Each model is available for sourcing through DriveKNMS.

Transmitter Power Supply / Signal Conditioners (4–20 mA)

• KFD2-STC4-EX1.H: 2-wire transmitter power supply, 1-channel, 4–20 mA output, HART transparent, Ex ia IIC
• KFD2-STC4-EX1: 2-wire transmitter power supply, 1-channel, 4–20 mA, without HART, Ex ia IIC
• KFD2-STC4-EX2: 2-wire transmitter power supply, 2-channel, 4–20 mA, Ex ia IIC
• KFD2-STC4-EX2.H: 2-wire transmitter power supply, 2-channel, HART transparent, Ex ia IIC
• KFD2-CD-EX1.32: Repeater power supply, 1-channel, 4–20 mA, loop-powered, Ex ia
• KFD2-CD-EX2.32: Repeater power supply, 2-channel, 4–20 mA, Ex ia IIC

Temperature / RTD / Thermocouple Inputs

• KFD2-UT2-EX1: Universal temperature transmitter interface, 1-channel, RTD/TC/mV/Ω input, 4–20 mA output
• KFD2-UT2-EX2: Universal temperature transmitter interface, 2-channel, RTD/TC input, 4–20 mA output
• KFD2-GUT-EX1.D: Universal temperature converter, galvanically isolated, 1-channel, DIN rail
• KFD2-TT2-EX1: Thermocouple input isolator, 1-channel, mV signal, 4–20 mA output, Ex ia

Discrete / Digital I/O Modules

• KFD2-SR2-EX1.W: Solenoid driver / switch amplifier, 1-channel, relay output, Ex ia, NAMUR input
• KFD2-SR2-EX2.W: Solenoid driver / switch amplifier, 2-channel, relay output, Ex ia, NAMUR input
• KFD2-DWB-EX2.D: Discrete input isolator, 2-channel, NAMUR/dry contact, transistor output
• KFD2-SOT2-EX2: Solenoid output driver, 2-channel, 24 VDC output, Ex ia, short-circuit protected
• KFD2-UFC-EX1.D: Universal frequency converter, 1-channel, pulse/frequency input, 4–20 mA output

Communication / Fieldbus Adapters

• KFD2-HMM-EX1.179.179: HART multiplexer module, 1-channel, integrates with asset management systems
• KFD2-BR-EX1.PA: PROFIBUS PA segment coupler / repeater, Ex ia, DIN rail mount

Sourcing Hard-to-Find & Obsolete KFD2 Parts

DriveKNMS maintains a dedicated inventory program for KFD2 series modules, including models that have transitioned to limited availability or managed end-of-life status. For facilities operating legacy DCS platforms (Honeywell TDC 3000, Yokogawa CENTUM CS, ABB Advant) where KFD2 modules are embedded in marshalling infrastructure, replacing individual failed modules without a full cabinet redesign is the operationally preferred approach. DriveKNMS sources KFD2 inventory through authorized distribution channels and verified secondary market suppliers, with full traceability documentation. All units are inspected against original Pepperl+Fuchs datasheets prior to dispatch. For obsolete or discontinued KFD2 variants, DriveKNMS provides cross-reference analysis to identify functional equivalents within the current Pepperl+Fuchs catalog (KFD3 series, RN series) or compatible third-party alternatives, with full technical comparison reports available on request.

Quality Control for the KFD2 Range

KFD2 modules incorporate internal backplane bus communication and precision analog signal paths that require function-specific test procedures beyond standard continuity checks. DriveKNMS applies the following verification protocol to all KFD2 units: (1) Visual inspection for PCB contamination, relay contact wear, and terminal block integrity. (2) Loop simulation using calibrated 4–20 mA source/sink instruments to verify input-to-output linearity across the full signal range. (3) HART communication verification using a HART communicator (e.g., Emerson 475) to confirm transparent pass-through on HART-capable variants such as the KFD2-STC4-EX1.H. (4) Isolation resistance testing between input, output, and power supply circuits per IEC 61010 requirements. (5) Functional relay output test for discrete I/O variants under rated load conditions. (6) Burn-in at rated operating temperature for a minimum of 24 hours prior to shipment on critical-application orders. Test records are retained and available for customer audit.