 Technical Data
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Connections for Sensor and Panels
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GDS Policy for Earth , zero volts and screen connections
for sensor and panels
Summary
Gas system Installations generally have many differing
methods of connection for Earth and screens and unfortunately
some can cause problems with the operation of equipment
through earth loops and signal noise. This document
therefore states the preferred method of connection
for land based and marine based GDS equipment .
Installation
non hazardous
Screened multi core cables should be used in preference
to non screened.
Power and signals can exist in the same multi
core cable.
The sensor electronics is floating and not connected
to the sensor enclosure. |
| Eg |
3 core plus screen for use with powered 4-20mA
sensors wired to a control panel.
core 1 is power from panel (usually 24v )
core 2 is zero volts from panel (0V)
core 3 is signal (source or sink to the control
panel)
screen is wired to zero volts at the panel only.
(ie do not connect screen at the sensor head
)
The sensor metal enclosure can be connected
to local earth (ie mains earth) or left
floating. Do not connect to zero volts. |
Installation
flameproof
Armoured multi core cables with screen should
be used in preference to non screened.
(note the Armour and the screen are separate
conductors)
Power and signals can exist in the same multi
core cable.
The sensor electronics is floating and not connected
to the sensor enclosure. |
| Eg |
3 core plus armour and screen for use with powered
4-20mA sensors wired to a control panel.
core 1 is power from panel (usually 24v )
core 2 is zero volts from panel (0V)
core 3 is signal (source or sink to the control
panel)
screen is wired to zero volts at the panel only.
(ie do not connect screen at the sensor head
)
Armour will be connected to the metal enclosure
via the gland and can be
connected to local earth. or left floating .
Do not connect to zero volts. |
Multi
drop Installations with data , flameproof
With networked sensors , a single cable is
used with 2 or more sensors connected in parallel
along the length of the cable.
Armoured multi core cables with screen should
be used in preference to none screened.
(note the Armour and the screen are separate
conductors)
Power and signals (usually data packets) can
exist in the same multi core cable.
A Twisted pair should be used for the data
signals.
The sensor electronics is floating and not
connected to the sensor enclosure. |
| Eg |
4 core plus armour and screen for use with
powered intelligent sensors wired to a control
panel.
core 1 is power from panel (usually 24v )
core 2 is zero volts from panel (0V)
core 3 is signal data + differential
core 4 is signal data - differential
screen is wired to zero volts at the panel
only.
(ie do not connect screen at the sensor head
except to make continuous through all sensors.
See diagram 3.)
Armour will be connected to the metal enclosure
via the gland and can be
connected to local earth. or left floating.
Do not connect to zero volts. |
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