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AS-i power supply units
Rule 2
To minimize the effects of voltage drops and to reduce cable costs, it is necessary
to determine the optimum power supply position on the bus, and also the minimum
cable cross-section appropriate for the distribution of power.
The voltage drop should not exceed 3V between the master and the last slave on
the bus. The table below lists the elements necessary for choosing the cross section
of the AS-i cable.
Table of characteristics:
AS-i cable cross-section
0.75 mm2
Linear resistance
52 milli Ohms/meter 27 milli Ohms/
meter
Voltage drop for 1A over 100 5.2V
meters
1.5 mm2
2.7V
2.5 mm2
16 milli Ohms/
meter
1.6V
The cable that meets the requirements for the majority of applications is the cable
with a 1.5 mm 2 cross-section. It is the standard model for the AS-i bus
(cable proposed by the SCHNEIDER catalog).
Cables of smaller cross-section can be used where the sensors consume very
little power.
Note: The maximum length without repeaters of all the segments making up the
AS-i bus is 100 meters. The lengths of cable connecting a slave to a passive
distributor must be taken into account.
35006196 03 October 2005
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