If it is electromagnetic interference from the air, it is generally necessary to make a metal meter box
outside the meter and ground the meter box at the same time.
If it is a four-wire meter, add an isolated power supply in the power supply section and a signal isolator
in the 4-20ma output section.
The left image of Figure 10 is the echo pattern under strong interference. The left to right in the picture
are high interference waves. In such cases, grounding does not solve all problems. At this time, it is
necessary to determine whether the interference comes from the power supply part or from the air.
If the ultrasonic level gauge's probe is retracted within the takeover, the takeover will amplify the
signal, which will cause some problems. Generally, there is a ratio between the height of the nozzle
and the diameter of the nozzle, which is 5: 3. Assuming the height is 200 mm, the diameter of the
If it is electromagnetic interference coming from the cable, especially the most used two-wire
ultrasonic level gauge, a passive signal isolator can be added in the middle to solve this interference.
Figure 11 The echo of the probe retracted into the tube
In the figure above, the bottom baseline of the echo becomes very wide, which is caused by the signal
being amplified by the takeover. The circles are real echoes, and the box is a particularly thick
baseline.
Figure 12 Echo after the probe is taken out
After taking out the ultrasonic level gauge from the inside, the baseline became significantly smaller
and returned to normal. The reflected wave inside the circle will be much higher than the baseline.
4.The Impact Of The Takeover On The Measurement
054
EN
7
0
1
7
8
7
2
.0
6
0
9
/2
0
1
8
C
H
/E
N
How To determine The cause Of a Field Failure Based On The Echo Graph
