2 Transmitter overview
2.1 Theory of operation
The Rosemount
™
5300 Level Transmitter is a smart, two-wire continuous level transmitter
based on Time Domain Reflectometry (TDR) principles. Low power nano-second-pulses
are guided along an immersed probe. When a pulse reaches the surface, part of the energy
is reflected back to the transmitter, and the time difference between the generated and
reflected pulse is converted into a distance, which calculates the total level or interface
level (see Figure 2-1).
The reflectivity of the product is a key parameter for measurement performance. The
reflection intensity depends on the dielectric constant of the product. Media with a high
dielectric constant gives better reflection (signal amplitude) and a longer measuring
range.
Signal amplitude thresholds are used to separate the measurement signal from disturbing
echoes and noise. The dielectric constant of the product is used for setting the
automatically calculated amplitude thresholds. See Adjusting thresholds for more
information about threshold principle.
For interface measurements the dielectric constant of the upper product is essential for
calculating the interface level.
Figure 2-1: Measurement Principle
A. Signal amplitude
B. Time
C. Reference pulse
D. Level
E. Interface level
Reference Manual Transmitter overview
00809-0100-4530 April 2019
Reference Manual 11
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