Figure 56 Com Loop Current Consumtion Vs. Cable Length - Panasonic Firetracker FT1020G3 CIE Technical And Programming Manual

Therefore, the maximum allowable distance
�� 42.3
������
�� = =
2 ( 0.0119 )
2��
��
If the temperature was raised to 80C, we would expect that the resistance will also
increase. The relationship between resistance and temperature is given by,
�� = �� [1 + �� (�� − ��
������ ���� ������
Where,
R = Resistance per unit
R = Resistance per unit at a reference temperature
ref
Coefficient of copper ��
T = Actual temperature
T = Reference temperature
ref
Hence, calculating for this gives:
�� = 0.0119[1 + 0.00323(80 − 20)] Ω/�� = 0.0142 Ω/��
Therefore, the new distance would be:
42.3
�� = = 1489 ��
2(0.0142)
1800
1600
1400
1200
1000
800
600
400
0 50

Figure 56 COM Loop Current Consumtion vs. Cable Length

The total COM loop unit current consumption is increased as the number of units are added
to a loop. Refer to "Current consumption" page 174 as details are given as to how much
current is consumed by each unit as they are added to the loop.
= 1777 ��
)]
= 0.00323
����
Maximum Cable Length
100 150 200
Total COM loop unit current consumption (mA)
171
Technical/Programming Manual
FT1020G3 Rev 2.2.1
Total COM Loop Unit
Current Consumption
(mA)
2
1.50mm Cable .
11.9Ω/Km
250 300 350
Use the FT1020G3