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Fig. 2 Echo Signals after Resonance Problem Solved
After the resonance problem is solved, the echo close to the left is obviously nar-
rower than that shown in Fig. 1 and the real echo can be recognized by the ultraso-
nic level gauge then.
8.2 Liquid enters the blind area of ultrasonic level gauge
Fig. 3 Echo Pattern after Liquid Enters Blind Area
The ultrasonic level gauge has a blind area at the position near the emitting surface
of probe. The blind area will increase with the increase of effective measuring distan-
ce. For example, the ultrasonic level gauge with a measuring range of 5m has a
0.50m blind area at 20 °C.
The echo enclosed by the red frame in figure above is the high-intensity echo caused
by blind area and the echo enclosed by red circle is normal echo signal. Due to
strong echo caused by blind area, the real echo signals on the right are covered and
the measured water level data may be any values. Seeing carefully, you may find
that the echo in blind area is similar to the echo caused by resonance in Fig. 1.
After we raise the installation position of probe to make the distance from the hig-
hest water level to the emitting surface of probe be greater than 0.50 (blind area),
we find that the echo close to probe on the left changes.