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57-642 ECLIPSE Model 705 Guided Wave Radar Transmitter for Hygienic Industries
The Damping parameter is not typically used in Life
Sciences applications. Most guided wave radar units are
connected to a PLC or DCS that has the capability to per-
form any damping while true measurement can be received
into data collection systems.
4.4.3 Strapping Tables
A bent probe creates a non-linear output relative to actual
liquid level in a vessel. To account for this non-linearity, the
MAGNETROL ECLIPSE unit has a twenty-point strap-
ping table embedded in the device that will correlate a mea-
sured level to some configurable point.
The most common method for using the strapping table in
Life Sciences applications is through a calibrated flow meter
(e.g., coriolis), filling the vessel to meter known volumes.
Then, entering the output level value into the table along
with the corresponding volume as measured by the meter.
Using the strapping table will not only compensate for the
non-linearity associated with bends in the probe, but also
will account for the changes in volume from changes in
tank geometry, disturbances such as agitator blades, and any
other dynamics along the probe.
The published repeatability for the MAGNETROL
ECLIPSE guide wave radar in typical Life Sciences applica-
tions is 0.025% of volume or 0.1" (3mm), whichever is
greater. It is important to note that the flow meter should
be operated at the rated flow-rate to make sure that the
meter does not affect the accuracy of the strapping table.
When preparing a strapping table, identify areas where there
is significant non-linearity of volume with respect to level.
Then, select and cluster strapping table points in quantities
of 3 to 5, depending on availability, around the identified
areas. For example, in a typical tulip-shaped tank, approxi-
mately fifty percent of the points should be in the non-lin-
ear portion of the tank. Then, 3-5 cluster points should be
assigned to the batch heights for the process.
Finally, one point should be reserved in any application for
a point at 105%-110% of the maximum operating volume.
There are two philosophies regarding the first point. Most
tables will perform linear interpolation between points.
Therefore, anything measured between zero and the first
strapping table point will be interpolated. However, some
users prefer to measure the first possible point and correlate
that to a known volume for repeatability.
