Zener Barrier

Z787

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.

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

300 Ω

Series resistance

terminals 1, 8: max. 327 Ω

Voltage drop

terminals 4, 5: 1.2 V + (36 Ω x signal current)

Fuse rating

50 mA

Hazardous area connection

Connection

terminals 1, 2; 3, 4

1

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Pepperl+Fuchs Group

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