Siemens SITRANS LR460 HART Operating Instructions Manual page 146

dielectric constant (DK): the ability of a dielectric to store electrical potential energy under the
influence of an electric field. Also known as Relative Permittivity. An increase in the
dielectric constant is directly proportional to an increase in signal amplitude. The value is
usually given relative to a vacuum /dry air: the dielectric constant of air is 1
echo: a signal that has been reflected with sufficient magnitude and delay to be perceived in
some manner as a signal distinct from that directly transmitted. Echoes are frequently
measured in decibels relative to the directly transmitted signal.
echo confidence: the recognition of the validity of the echo. A measure of echo reliability.
Echo Marker: a marker that points to the processed echo.
Echo Processing: the process by which the radar unit determines echoes.
Echo Strength: describes the strength of the selected echo in dB above 1 V rms.
Echo Profile: a graphical display of a processed echo.
emission cone: the extension of the antenna's angle
false echo: any echo which is not the echo from the desired target. Generally, false echoes are
created by vessel obstructions.
frequency: the number of periods occurring per unit time. Frequency may be stated in cycles
per second.
hertz (Hz): unit of frequency, one cycle per second. 1 Gigahertz (GHz) is equal to 10
horn antenna: a conical, horn-shaped antenna which focuses microwave signals. The larger
the horn diameter, the more focused the radar beam.
inductance: the property of an electric circuit by virtue of which a varying current induces an
electromotive force in that circuit or in a neighboring circuit. The unit is a Henry.
microwaves: the term for the electromagnetic frequencies occupying the portion of the radio
frequency spectrum from 1 GHz to 300 GHz.
multiple echoes: secondary echoes that appear as double, triple, or quadruple echoes in the
distance from the target echo.
Near Range: a blind zone extending away from the reference point plus any additional shield
length.The instrument is programmed to ignore this zone.
nozzle: a length of pipe mounted onto a vessel that supports the flange.
parameters: in programming, variables that are given constant values for specific purposes or
processes.
polarization: the property of a radiated electromagnetic wave describing the time-varying
direction and amplitude of the electric field vector.
1. Many conductive liquids/electrolytes exhibit dielectric properties; the relative
dielectric constant of water is 80.
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