VEGA Z728 Zener barriers - Manual (Page 23)

23
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
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Audible alarms
Audible alarms operate at relatively high voltages and low
currents. They are approved for use with various Zener barriers. The simplest solution is the circuit shown above.
I/P converters
The simplest and most cost-effective solution is a single-
channel Zener barrier. The nominal supply control voltage
must either be ground-free or connected to the negative output
to earth. In theory, the field circuit can have a resistance of 900 Ohm if the voltage supply is 27 V. In practice, however, the
voltage values are lower, so that the field circuit normally has a
resistance of 300 Ohm.
Hazardous area Safe area
Z728
x3
CL
1
2
8
7
Hazardous area Safe area
P
I
1
2
3
4
Z787
x3
x3
8
7
6
5