Sharp UP-810F Spécifications télécharger pdf (Page 187)

COMMUNICATIONS

Sharp Electronics Corporation

More on the Type Wire

Wire Gauge

The size of each wire is describes as the gauge size, and is measured in units of

American Wire Gauge (AWG). Below is a list of gages with a description of how

small or large that size is:

40 AWG smaller than a hair

30 AWG sewing thread

20 AWG diameter of a pin

10 AWG knitting needle

1 AWG pencil

1/0 "1-aught" finger

Resistance

The choice of metal, the gauge size of the wire, and the length of the wire can

determine the resistance of any conductor. Charts are available, such as in the back

pages of the Belden Master Catalog, which shows the resistance for stranded wire

from 36 AWG to 10 AWG, and the resistance for solid 40 AWG to 10 AWG.

All wire has resistance. Resistance affects the signal by turning part of the signal into

heat. This creates a voltage drop on the wire when one end is compared to the

other. The voltage drop can be determined by one of the formulas of Ohm’s Law, E

R, where E is the voltage drop on the wire, I is the current in amps, and R is the

resistance in ohms.

While a voltage drop in the presence of any resistance is unavoidable, picking a

larger conductor with lower resistance can reduce the effect. Also, resistance is

linear over frequency, meaning that resistance affects all frequencies equally. It is

therefore often ignored since the effect may be a minor drop in overall level.

Insulation

Basic insulation prevents wires from touching each other and creating a short circuit

or grounding portions of a circuit that should not be grounded.

Capacitance

A capacitor is a device that holds an electrical charge. It consists of two metal plates

with insulation in between. Well, isn’t that exactly what a cable is? Two metal plates

(or wires) with an insulator (dielectric) in between. Figure 9 shows the specific parts

of a twisted pair and coax cable that are involved with capacitance.

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Sharp UP-810F Spécifications Page 187