HBM SD01A Bedienungsanleitung Seite 10

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The Zener barrier can only limit the voltage and current in the intrinsically safe
circuit effectively if the energy stored in the intrinsically safe circuit is also
limited. Therefore the capacitance and inductance in this circuit, also taking
account of the cable properties, must not exceed defined values.
The SD01A Zener barrier set is intended for operating SG full-bridge
transducers on measuring amplifiers that have a symmetric excitation using
DC voltage or carrier frequency.
The Zener barriers therefore have a dual-channel construction, and the Zener
diodes are wired to make them suitable for AC voltage.
Grounding Zener barriers
The purpose of the dual-channel structure of the Zener barrier is not only to
limit the voltage and current between the two channels with terminals 5 and 8,
but also to make sure they are limited relative to the ground potential.
NOTE
In order to operate the barrier safely it must always be grounded
through a potential equalization line.
The cross-section of the ground connection in the case of a copper conductor
must be at least 4mm
12.2.4).
CAUTION
Double grounding of intrinsically safe circuits is not prohibited.
The isolation voltage of lines and field devices (load cells), measured against
ground, must be greater than 500 V AC.
CAUTION
In the case of cable lengths over 50 meters the shield must not be
put on on both sides.
HBM
2
(for further requirements see EN60079−14, section
SD01A
A1045−2.4 en/de/fr