Z728

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Zener Barrier for Galvanic Isolation for ATEX Zone

The Z728 is an intrinsically safe barrier that protects equipment located in ATEX zones by limiting the transmitted voltage and current, ensuring that no dangerous energy

can cause an explosion.

Zener Barrier for Intrinsic Safety in ATEX Zones

The Z728 is an intrinsically safe Zener barrier used in industrial installations located in ATEX zones (explosive atmospheres) to protect equipment and prevent the ignition of an explosive mixture. It is manufactured by the company Pepperl+Fuchs.

1. General Description

The Z728 is a single-channel Zener barrier that limits the electrical energy (voltage and current) sent to equipment installed in a hazardous area. Its role is to ensure that a fault occurring in the safe area cannot transmit enough energy to cause an explosion.

It is installed between the control system (safe area) and the field instrument located in the ATEX zone (sensor, detector, etc.).

2. Operating Principle

The barrier uses Zener diodes, a resistor, and a fuse:

Under normal operation, the voltage remains below the breakdown voltage of the Zener diodes.
In the event of an overvoltage or fault, the Zener diodes conduct the excess current to ground.
If the current becomes too high, the internal fuse (50 mA) opens the circuit.

This ensures that the energy transmitted to the hazardous area remains below the ignition level.

3. Typical Applications

The Z728 barrier is used with:

NAMUR sensors
Proximity detectors
Mechanical contacts
Industrial transmitters and sensors
Solenoid valves or relays installed in hazardous areas

It is commonly used in industries such as:

Oil and gas
Petrochemical plants
Chemical industry
Fuel storage depots
Pharmaceutical industries

4. Main Technical Characteristics

Characteristic	Value
Type	Single-channel Zener barrier
Operating voltage	≈ 26.5 V
Maximum safety voltage	28 V
Maximum current	93 mA
Series resistance	≈ 300 Ω
Internal fuse	50 mA
Mounting	DIN rail
Operating temperature	−20 to +60 °C
Protection rating	IP20