Vortex
71
APPENDIX F: EARTHING
Introduction
The following decision tree and the accompanying diagrams can be used to establish the
earthing needed for your system.
Definitions
Intrinsic Safety
Earth
The earthbar connection to the zener barriers. It should have its own
unique cable connection back to a central grounding point.
Isolated power
supply
A power supply where the 0V line is not connected to the earth
terminal.
The internal power supply in Vortex is isolated.
Galvanic isolator An alternative to a zener barrier that does not require the high
integrity earth.
Zener barrier
A device used to implement a safe interface between a safe and a
hazardous area. The device limits the amount of voltage and current
that can enter the hazardous area, in order that sparks or heat caused
by an electrical fault in the safe area do not cause an ignition hazard in
the hazardous area. Zener barriers require a high integrity earth
(ground) connection, sometimes known as the Intrinsic Safety Earth.
Questions
These questions are referred to in Figure 20 The possible answers are also listed. Answer the
questions and follow the tree until it refers to the diagrams which should be used as a guide to
wiring and earthing requirements.
Question no. Question
How many sensors require the use of zener barriers OR
galvanic isolators?
NONE
SOME
ALL
2
Does the system use the Vortex internal mains to DC
power supply?
YES
NO
3
Is the external mains to DC power supply isolated? YES
NO
4
Is the safe area interface via a zener barrier device? YES
NO
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