VEGA Z728 Zener barriers - Manual (Page 17)

17
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
SMART transmitter
The simplest possible solution is the use of a 2-channel Zener
barrier with 28 V, 300 Ohm and 28 V diode return. If a
regulated power supply unit provides an output voltage of 27 V,
13.9 V will be available to the transmitter and wiring in the Ex-
area. The data transfer is bidirectional, so that a non-certificated
communicator can be connected and used in the the safe area.
The system is approved for [EEx ia] IIC.
Strain gauge bridges
The strain gauge bridge is supplied via the Z966. The Z966
enables a 350 Ohm strain gauge bridge to be supplied with
8 V. The voltage feedback via the Z964 can be dispensed with,
although in practice most applications require this feedback to obtain the best possible accuracy of measurement.
The millivolt signal is transferred to the safe area via the Z964.
The system is approved for [EEx ia] IIC.
Hazardous area Safe area
Z787
A
8
7
6
5
1
2
3
4
x3
x3
Hazardous area Safe area
Signal
Z966
x3
x3
x3
x3
1
2
3
4
8
7
6
5
Z964
x3
x3
x3
x3
1
2
3
4
8
7
6
+
-
5
Z964
x3
x3
x3
x3
1
2
3
4
8
7
6
5