HP 34970A manual 332

Chapter 8 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).

AWG	W / ft (2 conductors)
	at 25 °C
14	5 mΩ
16	10 mΩ
18	15 mΩ
20 *	20 mΩ
22	30 mΩ
24	50 mΩ

*Recommended wire size for the screw terminals on HP 34970A 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.

Cable Type	Nominal Impedance	Capacitance	Attenuation
Twisted Pair	100Ω at 1 MHz	10 to 20 pF/ft	Up to 1 dB/100 ft at 1 MHz
Shielded Twisted Pair	100Ω at 1 MHz	10 to 20 pF/ft	Up to 1 dB/100 ft at 1 MHz
Coaxial	50Ω or 75Ω at 100 MHz	15 to 25 pF/ft	Up to 6 dB/100 ft at 100 MHz
Twisted Pair Ribbon	100Ω at 1 MHz	15 to 20 pF/ft	Up to 1 dB/100 ft at 1 MHz

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