KROHNE OPTITEMP TT 51 EN - Manual (Page 24)

4
ELECTRICAL CONNECTIONS
24
TT 51 SERIES
www.krohne.com 09/2010 - 4000754201 - MA TT 51 R01 en
For multiple connections (Multidrop mode), the following formula shall be used:
L = [(65 x 10
6
) / R x C)] x (Cn x 5000 + 10000) / C
with
L: cable length [m or ft]
R: load resistance (incl. the resistance of any Zener barrier) + cable resistsance [Ω]
C: cable capacitance [pF/m or pF/ft]
Cn: number of transmitters in the loop
Insulation Capacitance [pF/m]
PVC 300...400
Polyethylene 150...200
Polyethylene foam 75...100
Conductors Resistance [Ω/km]
(both conductors in series)
Area [mm
2
]
Diameter [mm] AWG
2.0 1.6 14 17
1.3 1.3 16 28
1.0 1.15 17 36
0.8 1.0 18 45
0.5 0.8 20 70
0.3 0.6 22 110
0.2 0.5 24 160
Table 4-2: Cable parameters