User`s guide
258
Chapter 7 Tutorial
System Cabling and Connections
• Cable Resistance – Varies with wire gauge size and cable length. Use
the largest gauge wire possible and try to keep the cable lengths as
short as possible to minimize the cable resistance. The following table
lists typical cable resistance for copper wire of several gauge sizes
(the temperature coefficient for copper wire is 0.35% per °C).
* Recommended wire size for the screw terminals on 34970A/34972A plug-in
modules.
• Cable Capacitance – Varies with the insulation type, cable length,
and cable shielding. Cables should be kept as short as possible to
minimize cable capacitance. In some cases, low-capacitance cable can
be used.
The table below lists typical cable specifications.
AWG
ft (2 conductors)
at 25 °C
14
16
18
20 *
22
24
5 m
10 m
15 m
20 m
30 m
50 m
Cable Type Nominal Impedance Capacitance Attenuation
Twisted Pair 100 at 1 MHz 10 to 20 pF/ft Up to 1 dB/100 ft at 1 MHz
Shielded Twisted Pair at 1 MHz 10 to 20 pF/ft Up to 1 dB/100 ft at 1 MHz
Coaxial 50or 75 at 100 MHz 15 to 25 pF/ft Up to 6 dB/100 ft at 100 MHz
Twisted Pair Ribbon 100 at 1 MHz 15 to 20 pF/ft Up to 1 dB/100 ft at 1 MHz
34970A Refresh UG.book Page 258 Wednesday, February 17, 2010 12:34 PM