Siemens SITRANS LUT400 Operating Instructions Manual page 292

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
HART: Highway Addressable Remote Transducer. An open communication protocol used to
address field devices.
multiple echoes: secondary echoes that appear as double, triple, or quadruple echoes in the
distance from the target echo.
parameters: in programming, variables that are given constant values for specific purposes or
processes.
range: distance between a transducer and a target.
shot: one transmit pulse or measurement.
speed of sound: the speed at which sound is propagated through some medium under
specified conditions.
stillpipe: a pipe that is mounted inside a vessel parallel to the vessel wall, and is open to the
vessel at the bottom.
stilling well: see stillpipe.
TVT (time varying threshold): a time-varying curve that determines the threshold level above
which echoes are determined to be valid.
Page 284 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS
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Hz.
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