Civil Engineering Reference
In-Depth Information
Fig. 2.28
Simplified equivalent to calculate the maximum allowed cable length of a star
topology
It is possible using the voltage divider formula to calculate the maximum allowed
cable resistance (and with it the maximum allowed cable length) under the con-
sumption that the voltage drop over the receiver resistances is 0.9 V or higher [2.4]:
V
Kabel
)
⋅
R
(
Term b
_
V
out
diff
R
=
(2.4)
Kabel
max
V
1
−
Kabel
⋅ 2
(
)
V
out
diff
Considering a star topology, the resistance arrangement and with it the simplified
equivalent circuit change to that shown in Fig.
2.28
.
At a daisy chain topology, thus a linear topology with stub length of 0 m, an
iterative calculation helps calculating the maximum allowed cable length as shown
in Fig.
2.29
.
