Rheonics | Switzerland | U.S.A.
SRV, SRD, SRV-FPC, SRD-FPC Installation and Intrinsic Safety Manual
P. 19
Version 2.0, Updated: October 29, 2020
Rheonics GmbH, Klosterstrasse 19, 8406 Winterthur, Switzerland
©Rheonics. Rheonics confidential and proprietary information.
Table 5: Pt1000 circuit(s) Zener diode barrier specifications
Max. output voltage
Uo
< 9
V
Min. output resistance
Ro
> 1950
Ohm
Max. output current
Io
< 5
mA
Max. output power
Po
< 10
mW
Fuse rating
<=80
mA
For a 3-wire connection, a single barrier may be used, with the third (grounding) lead of the
Pt1000 circuit connected to ground through the cable shield. For a 4-wire connection, two Zener
diode barriers must be used, with two wire connected to each of the two channels of the Zener
diode barriers.
The Zener diode barriers must be located outside of the hazardous zone, or in a zone allowed by
the manufacturer’s specification
. They must be properly grounded.
Commercial Zener diode barriers that fulfill these specifications are:
For transducer coil circuit:
P Fuchs Z757
Table 6: Specification of commercial Zener diode barrier suitable for transducer coil circuit
Series resistance
9.8 ohms, min.
Fuse rating
200 mA
Maximum safe voltage
250 V
Output voltage, U
o
7.14 V
Output current, I
o
729 mA
Output power, P
o
1.3W
For Pt1000 circuits (1 or 2 units depending on whether 3 or 4 wire connections are used):
P Fuchs Z041
Table 7: Specification of commercial Zener diode barrier suitable for Pt1000 circuit(s)
Series resistance
1957 ohms, min.
Fuse rating
80 mA
Maximum safe voltage
250 V
Output voltage, Uo
8.61 V
Output current, Io
4 mA
Output power, Po
9.4 mW
