Siemens SITRANS LG270 Operating Instructions Manual page 19

standpipe. When designing the standpipe, keep the upper blocking
distance of the probe in mind and plan the length above the upper
lateral filling opening accordingly.
Microwaves can penetrate many plastics. This is why plastic tubes are
problematic for measurement applications. If durability is no problem,
we recommend the use of uncoated metal standpipes.
When the SITRANS LG270 is used in standpipes, contact with the
tube wall must be avoided. We recommend for this purpose a cable
probe with centering weight.
Caution:
When mounting, make sure that the cable is straight over its entire
length. A kink in the cable can cause measurement errors and contact
with the tube.
With rod probes, a spacer is generally not required. However, if there
is a risk of the rod probe being pressed against the tube wall by in-
flowing medium, you should mount a spacer at the probe end to avoid
contact with the tube wall. In the case of cable probes, the cable can
be strained.
Keep in mind that buildup can form on the spacers. Strong buildup
can influence the measurement.
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PBD-51041064 SITRANS LG270 - Operating Instructions