Pepperl+Fuchs Z778 Zener barrier intrinsically safe

The Pepperl+Fuchs Z778 is a Zener barrier designed for intrinsically safe (IS) applications, providing protection for 4–20 mA analog signals in hazardous areas (e.g., Zone 1/21, Zone 2/22). It ensures safe signal transmission between field devices (sensors/transmitters) and control systems by limiting voltage and current to non-incendive levels.

Key Features of the Z778 Zener Barrier

✔ Single-Channel (1-Channel) Isolation – Protects one 4–20 mA loop.

✔ Zener Diode-Based Safety – Limits energy to Ex ia IIC / Ex ib IIC standards.

✔ Approvals:

ATEX / IECEx (Ex ia IIC T6 Ga / Ex ib IIC T6 Gb)

FM / CSA (Class I, II, III, Div. 1)

✔ Input Voltage: 20–3

✔ LED Diagnostics – Indicates power and fault conditions.

✔ Compact Design – DIN-rail mountable (standard 35mm rail).

Typical Applications

Process automation (4–20 mA transmitters in hazardous zones).

Oil & gas, chemical plants, pharmaceutical industries.

Intrinsically safe temperature/pressure sensor interfacing.

Wiring & Installation

Safe Area (Control Side)

Terminals 1 (+Ub): Power supply (20–30V DC).

Terminals 2 (GND): Ground connection (must be properly bonded).

Terminals 3 (OUT): Signal output to PLC/DCS.

Hazardous Area (Field Side)

Terminals 4 (IS+): Intrinsically safe output to field device.

Terminals 5 (IS–): Return line from field device.

⚠ Critical Safety Note:

Zener barriers require a solid earth ground (<1 Ω) for proper operation.

Faulty grounding can compromise intrinsic safety!

Comparison with Other Pepperl+Fuchs Barriers

Model Type Channels Key Difference

Z778 Zener Barrier 1 4–20 mA, Ex ia/ib IIC

KFD2-SR2-Ex2 Galvanic Isolator 2 Higher isolation, no ground dependency

LB Series Loop-Powered 1/2 For 2-wire transmitters

Why Choose the Z778?

✅ Ensures compliance with ATEX/IECEx/FM/CSA in explosive atmospheres.

✅ Simple, cost-effective protection for analog signals.

✅ Robust DIN-rail mounting for industrial panels.