Brooks Firetracker FT128 CIE - Table 16 Distance Away from CIE that Display Units Can be Located

Technical / Programming Manual
FT128 Rev 2.2
167
Table 16 Distance away from CIE that Display Units can be located.
Cable
Type
BAC0898
SMA2704
Wire Resistance Ru
at 20° C
11.9
Ω/Km
Wire Resistance Ru
at 20° C
21
Ω/Km
c.s.a. of cable = 1.5mm²
c.s.a. of cable = 1mm²
Unit
1728
1736
1728
1736
Iunit (A)
0.088
0.079
0.088
0.079
Vbatt (V)
12
12
12
12
No. of
units
Allowed
cable
resistance
Rallowed
(Ω)
Max.
distance
from
CIE, D
(metres)
Allowed
cable
resistance
Rallowed
(Ω)
Max.
distance
from
CIE, D
(metres)
Allowed
cable
resistance
Rallowed
(Ω)
Max.
distance
from
CIE, D
(metres)
Allowed
cable
resistance
Rallowed
(Ω)
Max.
distance
from
CIE, D
(metres)
8
17.05
1200
18.99
1200
17
812
19
904
7
19.48
1200
21.70
1200
19
928
22
1033
6
22.73
1200
25.32
1200
23
1082
25
1200
5
27.27
1200
30.38
1200
27
1200
30
1200
4
34.09
1200
37.97
1200
34
1200
38
1200
3
45.45
1200
50.63
1200
45
1200
51
1200
2
68.18
1200
75.95
1200
68
1200
76
1200
1
136.36
1200
151.90
1200
136
1200
152
1200
Table 16 was tabulated based on the calculation example given previously under the same
conditions described above. This pre-calculated table serves as a quick estimate for the
cable length to the number of Display Units that can be used depending on the selected
cables.
If a cable with a reduced conductor area is used, the wire resistance (Ω / Km) will be higher
and the possible cable length will be shorter. The display units RS485 bus uses RS485
communications standard. Therefore, the maximum distance from the CIE for any number
of Display Units should not exceed 1200 metre even though calculations show otherwise.