• Use the probe end echo as reference when the surface echo is close to the probe end to
enhance accuracy of the surface echo position.
By using the Probe End Projection function, the device is capable of measuring the product
level even if the surface echo is lost. The Probe End Projection is suited for challenging
applications with very poor reflectivity (low dielectric constant). Due to the poor
reflectivity of the product, situations may occur where the surface pulse is invisible to the
transmitter at long measuring ranges.
If the surface becomes invisible, the device will revert to use the probe end, and the most
recently estimated value of the dielectric constant to calculate the surface. Once the
surface reappears, the device will immediately use direct measurement on the surface
again. The calculated surface value is less accurate than the value with direct
measurement.
When the microwaves emitted by the Rosemount 5300 Transmitter propagate through
the product in the tank, the probe end echo appears to be located below the actual probe
end. The apparent displacement of the probe end echo peak is a consequence of the
reduced propagation speed of the measurement signal through the product compared to
the speed through air. The displacement of the probe end pulse can be observed by using
the Echo Curve Analyzer in the Rosemount Radar Master (see Use the echo curve analyzer
in Rosemount Radar Master).
For products with very low dielectric constants the product surface level can be
determined by comparing the actual probe end position as given by the Probe Length
value, with the apparent position of the probe end echo peak. The difference is related to
the properties of the product, i.e. the Dielectric Constant, and the distance D travelled by
the measurement signal through the product, see Figure D-2.
Reference Manual Advanced configuration
00809-0100-4530 April 2019
Reference Manual 399
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