MP200 Installation Manual
25
10.1 SECTION SIZING OF CONDUCTORS SUPPLYING A
SENSOR OR AN ACTUATOR (IN D.C.)
• The purpose of this paragraph is to offer a method for calculating the section of cables that supply a sensor or
an actuator. As well as defining the battery capacity and defining the current to be supplied by the power supply
unit, the correct size for cable section ensures that devices receive the best voltage values, in line with criteria
laid down by the manufacturer. A sensor or an actuator that is supplied with a lower value than the minimum
declared means that the device will risk instability, lack of efficiency and poor protection from interference.
10.1.1 Procedure
• A series of parameters are involved in creating the quality of the power line (screening section, connections,
welding, etc). The objective is to size the cable section that make up the line between the source (for instance
the control unit, the power supply unit, a junction) and a load (for instance a sensor, a siren, a junction).
• There follows a list of some of the data that should be read:
Source
power
Vs
13V
Minimum
power
for the load
Vc
11.5V
Load
consumption
Ic
10mA
Length of the
line
L
5 0 m
• When the data has been obtained, use it in a simple formula to obtain the size of the smallest cable section
possible for ensuring best functioning: minimum section Sm, expressed in square millimetres must be greater
than or equal to:
Sm
(L x Ic x 0.038) : [ (VS - Vc) x 1000]
• In the example:
Sm
(50 m x 10 mA x 0.038) : [{13V-11,5V) 1000) = 0.012 mm
2
The cable for our installation must therefore have conductors with a section greater than or equal to
0.012 mm
2
.
10.0 Conductor Sizing
source
load
for a correct result it is preferable to consider
a critical situation such as a mains power
failure.
read from the manufacturer's data, for
instance 11.5:15, read the lowest value in
the range
read from the plaque data or measured with
a multimeter (in milliamperes)
NOTE: if the devices are NOT self-powered,
use the highest consumption (when idle,
during an alarm, on stand-by)
length of cable laid between the source and
the load (in metres)
Summary of Contents for MP 200
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