INOR IPAQ R520X - Manual (Page 24)

4 ELECTRICAL CONNECTIONS C520/C520X / R520/R520X
09/2010 • 86B5200001 www.inor.com 24
To calculate the maximum cable length for the output circuit, determine the total resistance of
the output loop (load resistance plus the approximate cable resistance). Find out the
capacitance of the cable being used. In the tables below you can find the maximum cable length
based on the typical values for 1 mm 2 cables. CN is the abbreviation for Capacitance Number
which is multiple of 5000 pF present in the device.
Field device
Cable insulation
PVC Polyethylene Polyethylene foam
1 (CN = 1) 600 m 1100 m 2000 m
10 multi-drop (CN = 1) 500 m 900 m 1600 m
10 multi-drop (CN = 4,4) 85 m 150 m 250 m
Table 1: Maximum length for typical 1 mm 2 cables
Insulation Capacitance
PVC 300…400 pF/m
Polyethylene 150…200 pF/m
Polyethylene foam 75…100 pF/m
Conductors
Resistance
(both conductors in serie)
Area Diameter AWG
2.0 mm 2 1.6 mm 14 17 Ω/km
1.3 mm 2 1.3 mm 16 28 Ω/km
1.0 mm 2 1.15 mm 17 36 Ω/km
0.8 mm 2 1.0 mm 18 45 Ω/km
0.5 mm 2 0.8 mm 20 70 Ω/km
0.3 mm 2 0.6 mm 22 110 Ω/km
0.2 mm 2 0.5 mm 24 160 Ω/km
Table 2: Cable parameters
For multiple connections (multi-drop see the Figures 16), the following formula shall be used
L: Cable length (m)
R: Load resistance (incl. The resistance of any Zener barrier) + cable resistance ( Ω)
C: Cable capacitance/meter (pF/m)
Cn: Number of C520/R520 transmitters in the loop
Cable length can be changed to ft. The capacitance has to be specified in pF/ft.