VEGA Z728 Zener barriers - Manual (Page 16)

16
Zener barriers - operating instructions
Application examples
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group • Tel.: Germany +49 621 776-0 • USA +1 330 4253555 • Singapore +65 67799091 • Internet http://www.pepperl-fuchs.com
Da
te of issu
e
05/2
3
/03
0 mA … 20 mA/4 mA … 20 mA transmitter
This system can be used if the field device requires a relatively
high voltage. A 250 Ohm resistance is connected in parallel
with the Ex-output of the 10 V/50 Ohm output of this 2-channel barrier. Thus a voltage of 15.5 V is available at the field device
if the voltage supply is 27 V. The system is approved for
[EEx ia] IIC.
The combination of a 28 V, 300 Ohm and a 28 V barrier with
diode return is the solution for applications with 3-wire
transmitters. Special attention must be paid here to the internal voltage drop. The reason for this is the diode return. The
system is approved for [EEx ia] IIC.
Hazardous area Safe area
Z788.R
x3
x3
1
2
3
4
8
7
6
5
V
Hazardous area Safe area
Z787
x3
x3
x3
1
2
3
4
8
7
6
5
A