Configuration Manual Owner manual

Publication 1757-PM002A-EN-E - June 2006
2-8 Set Up A System
Additionally, power conditioners may have an internal terminator which
should be considered when placing terminators on the network.
Signal Wire Polarity
The combination signal/power wires have a plus (+) and minus (-) polarity
associated to the power conditioner outputs, which must be wired to the
appropriate terminals on the devices. Some devices are polarity insensitive,
meaning they still work if you connect the positive wire to the negative
terminal, and vice-versa.
Grounding
Follow all international, national and local codes for grounding and bonding
equipment. Above all, follow the manufacturer’s instructions and
recommendations for each device installed in a plant.
To prevent ground loops, a Fieldbus segment should only be grounded at one
point. This is usually done by grounding the cable shield at the control room
end of the segment.
Each process installation has a different requirement for grounding. Be sure
that the shield is electrically isolated from the transmitter housing and other
grounded fixtures.
Limiting Factors
Bus powered devices usually require 10-30ma of current and between 9-32
volts. The number of bus powered (two-wire) devices on a segment is limited
by the following factors:
• Output voltage of the fieldbus power supply
• Current consumption of each device
• Location of the device on the network/segment
• Location of the fieldbus power supply
• Resistance of each section of cable
• Minimum operating voltage of each device
IMPORTANT
Signal wiring of the fieldbus segment cannot be grounded.
Grounding out one of the signal wires will shut down an
entire fieldbus network.