Zener Barrier

Z787.H

Function

The Zener Barrier prevents the transfer of unacceptably high energy from the safe area into the hazardous area.

The zener diodes in the Zener Barrier are connected in the reverse direction. The breakdown voltage of the diodes is not exceeded in normal

operation. If this voltage is exceeded, due to a fault in the safe area, the diodes start to conduct, causing the fuse to blow. The Zener Barrier has a

positive polarity, i. e. the anodes of the zener diodes are grounded.

This high power version has a smaller serial resistance and therefore provides higher voltage to the field device.

The Zener Barrier is for evaluation of signals from the hazardous area. The diodes of diode return prevent a current into the hazardous area,

therefore the current assumption for intrinsic safety calculations is zero.

Depending on the application, increased or decreased intrinsic safety parameters apply for serial or parallel connection. For the detailed

parameters refer to the Zener Barrier certificate. Application examples can be found in the system description of the Zener Barriers.

Connection

3

1

6

8

2

7

4

5

Zone 2

Div. 2

Zone 0, 1, 2

Div. 1, 2

+

-

x3

x3

x3

Technical Data

General specifications

Type

DC version, positive polarity

Electrical specifications

Nominal resistance

240 Ω

Series resistance

max. 250 Ω

Fuse rating

80 mA

Hazardous area connection

Connection

terminals 1, 2; 3, 4

1

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Pepperl+Fuchs Group

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