Siemens SITRANS LG270 Operating Instructions Manual page 18

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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 bypass tubes, 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 the lower dead zone underneath the spacer in-
creases if spacers are used.
Buildup can form on the spacers. Strong buildup can influence the
measurement.
Fig. 9: Mounting in a bypass tube - Position of the spacer or the centering weight
1 Rod probe with spacer (steel)
2 Cable probe with centering weight
h Measurable tube section
Note:
Measurement in a standpipe is not recommended for extremely adhe-
sive products. In case of slight buildup, you should choose a bypass
tube with bigger diameter.
SITRANS LG270 - Operating Instructions
1
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PBD-51041506