Tektronix 1502C Service Manual page 242

Glossary
Aberrations
AC
Accuracy
Cable
Cable Attenuation
Cable Fault
Capacitance
Characteristic Impedance
1502C MTDR Service Manual
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Imperfections or variations from a desired signal. In TDRs, a pulse of electrical
energy is sent out over the cable. As the pulse-generating circuitry is turned on and
off, the pulse is often distorted slightly and no longer is a perfect step or sine-shaped
waveform.
Alternating current is a method of delivering electrical energy by periodically
changing the direction of the flow of electrons in the circuit or cable. Even electrical
signals designed to deliver direct current (DC) usually fluctuate enough to have an
AC component.
The difference between a measured, generated, or displayed value and the true value.
Electrical conductors that are usually insulated and often shielded. Most cables are
made of metal and are designed to deliver electrical energy from a source (such as
a radio transmitter) across a distance to a load (such as an antenna) with minimal
energy loss. Most cables consist of two conductors, one to deliver the electrical
signal and another to act as a return path, which keeps both ends of the circuit at
nearly the same electrical potential. In early electrical systems and modern systems
that over long distances use the earth and/or air as the return path, and the term
"ground" or "ground wire" is often used to describe one of the wires in a cable pair.
The amount of signal that is absorbed in the cable as the signal propagates down it.
Cable attenuation is typically low at low frequencies and higher at high frequencies
and should be corrected for in some TDR measurements. Cable attenuation is
usually expressed in decibels at one or several frequencies. See also: dB and Series
Loss.
Any condition that makes the cable less efficient at delivering electrical energy than
it was designed to be. Water leaking through the insulation, poorly mated
connectors, and bad splices are typical types cable faults.
(see Reactance)
Cables are designed to match the source and load for the electrical energy that they
carry. The designed impedance is often called the characteristic impedance of the
cable. The arrangement of the conductors with respect to each other is the major
factor in designing the impedance of cables.
Glossary–1