Glossary
Glossary
Aberrations
Imperfections or undesired variations in a signal. For example, aberrations in a TDR's excitation
signal are the result of the finite switching speed of the instrument's electronics and cause it to
deviate from a perfect step signal.
AC
Alternating current, a method of delivering electrical energy by periodically changing the direction
of the electric field in a conductor.
Accuracy
The difference between a measured or estimated value of a quantity and its true value. Accuracy
and precision are both important factors to consider when assessing the reliability of a
measurement.
Analog
Refers to a signal that is continuous with respect to both time and value. Analog circuitry
produces and/or measures analog signals. This is in contradistinction to digital signals, which are
discontinuous in both time and value. The sampling circuitry of a TDR converts the analog
voltage signal detected on a cable to a digital value for representation on the display and in the
instrument's memory.
Cable
Conductors of electricity that are usually shielded and insulated. Cables typically contain at least
two conductors, one to deliver the electrical signal and one to act as the return path. The
conductor acting as the return path may be referred to as the “shield,” “ground,” or “ground wire.”
A cable with such a ground return path is known as an unbalanced cable, an example of which is
typical coaxial cable. Another general type of cable is called balanced cable, an example of which
is twisted pair Ethernet cable. In balanced cable, two signal wires carrying differential signals of
opposite polarity are both separated from ground by an equal impedance.
Cable Attenuation
A quantity describing the energy in a signal that is absorbed, reflected, or otherwise lost during
propagation through a cable. Higher frequencies are typically the most susceptible to attenuation.
Cable attenuation can distort some TDR measurements. Attenuation is often expressed in
decibels (dB) at one or more frequencies. See also dB and Return Loss.
Mohr CT100 / CT100HF Operator's Manual 109
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