Inside the Pepperl+Fuchs KCD2-STC-Ex1 SMART Transmitter Power Supply: HART-Passing Isolation for 4-20 mA Field Loops

Pepperl+Fuchs KCD2-STC-Ex1 is a single-channel isolated barrier for intrinsically safe 4-20 mA instrumentation. It can power a two-wire transmitter in the hazardous area or accept a separately powered current source, then transfer the measurement to the non-hazardous control side. The module is designed for applications where analog isolation and bidirectional SMART communication must coexist in one compact K-System device.

From Field Transmitter to Control System

On the field side, KCD2-STC-Ex1 supplies the connected transmitter and receives its 4-20 mA measurement. The isolated output can be configured by DIP switches as a current source, current sink, or 1-5 V voltage source. This allows the barrier to match several types of DCS, PLC, recorder, and analog input arrangements without changing the basic field loop.

Why HART Communication Still Matters During Maintenance

HART data travels as a modulated signal superimposed on the analog current. KCD2-STC-Ex1 supports communication in both directions, so technicians can read device variables, check diagnostics, or adjust a compatible SMART transmitter from the safe side when the complete loop is correctly designed. If the loop resistance is too low for reliable communication, an internal 250 ohm resistance can be selected. Test sockets are integrated into the terminals for connecting a communicator.

Do Not Select by Housing Alone

Several Pepperl+Fuchs transmitter power supplies share a similar narrow housing. The suffix and terminal arrangement can indicate different approvals, outputs, diagnostics, or connection technology. Before replacing KCD2-STC-Ex1, confirm the entire label, field device type, required output mode, HART resistance, terminal numbers, Power Rail supply, and intrinsic-safety entity parameters. A visually similar module is not automatically an electrical substitute.

Applications That Benefit from This Arrangement

Typical loops include pressure, flow, level, density, and temperature transmitters in oil and gas facilities, chemical plants, refineries, water treatment systems, power generation, pharmaceutical production, and marine or offshore projects. The module can be used in new control panels, shutdown maintenance, loop modernization, and exact-model replacement where the installed transmitter must remain accessible through HART.

• Confirm whether the field device is two-wire or separately powered.

• Check whether the control input needs source, sink, or voltage mode.

• Review loop resistance before enabling the internal HART resistor.

• Compare the installed certificate and hazardous-area classification.

• Keep the exact code KCD2-STC-Ex1 on the purchase order.

Related models for comparison: KCD2-STC-1, KCD2-STC-Ex1.SP, KCD2-STC-Ex1-Y1, KCD2-STC-Ex1.2O, KCD2-STC-Ex1.ES, KCD2-STC-Ex1.ES.SP, KFD2-STC5-Ex1, KFD2-STC5-Ex2, KFD2-CRG2-Ex1.D, KFD2-SCD2-Ex1.LK, KFD2-UT2-Ex1, KFD2-SR2-Ex2.2S, KFD2-EB2, KFD2-EB2.SP, and HiC2025.

For a faster quotation, send the model, quantity, destination country, requested delivery date, and a clear product-label photograph. Sunup-MTL can assist with Pepperl+Fuchs barrier sourcing, model confirmation, export packing, and global shipping.