Pepperl+Fuchs Z728 Zener Barrier single-channel

The Pepperl+Fuchs Z728 is a compact, single-channel Zener barrier designed for intrinsically safe (IS) applications, specifically protecting NAMUR proximity sensors and mechanical contacts in hazardous areas (Zone 1/21, Zone 2/22). It ensures safe signal transmission between field devices and control systems by limiting energy to non-incendive levels.

Key Features of the Z728 Zener Barrier

✔ NAMUR Sensor Protection – Designed for proximity sensors (EN 60947-5-6) and mechanical contacts

✔ Intrinsic Safety Certifications:

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

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

✔ Electrical Specifications:

Supply Voltage: 8V DC (typical for NAMUR sensors)

Output: Relay contact or transistor (configurable)

Max. Field Current: ~8 mA (for NAMUR compliance)

✔ LED Status Indicator – Visual power/signal monitoring

✔ DIN-Rail Mountable – Compact 17.5mm width

Typical Applications

Hazardous area proximity sensing (oil/gas, chemical plants)

Limit switch monitoring in explosive atmospheres

Intrinsically safe sensor interfaces (Zone 1/21)

Wiring & Installation

Safe Area (Control Side)

Terminal 1 (+Ub): Power supply (typically 8V DC for NAMUR)

Terminal 2 (GND): Mandatory earth ground (<1Ω required)

Terminal 3 (OUT): Signal to PLC/controller

Hazardous Area (Field Side)

Terminal 4 (IS+): To NAMUR sensor/contact

Terminal 5 (IS–): Return line

⚠ Critical Notes:

Grounding is mandatory – Zener barriers require proper earthing.

For NAMUR sensors only – Not for standard 24V DC sensors.

Comparison with Similar Barriers

Model Type Key Difference

Z728 NAMUR/Contact Barrier For proximity sensors

Z715 Digital Barrier 24V DC discrete signals

KFD2-SR2-Ex2 Galvanic Isolator No ground needed

Why Choose the Z728?

✅ Specialized for NAMUR sensors in Ex zones

✅ Globally certified (ATEX, IECEx, FM, CSA)

✅ Compact and easy to install