Ultrasonic liquid level meter failure causes and solutions
2024-05-07
1. When entering the blind area of the instrument, the digital display may appear full scale or arbitrary data.
Fault cause
Ultrasonic level meter has a blind area, generally within 5 meters of the range, the blind area is 0.3-0.4 meters. The range within 10 meters is 0.4-0.5 meters. After entering the blind area, the ultrasound will appear arbitrary values and cannot work normally.
Solution skills
The height of the blind area should be considered when installing, and the distance between the probe and the highest water level must be greater than the blind area after installation.
2. The liquid fluctuation is relatively large when there is stirring in the field container, which will affect the measurement of the ultrasonic level meter. At this time, the instrument has no signal or the data fluctuates greatly.
Fault cause
The ultrasonic level meter said to measure a few meters away refers to the calm water surface. For example, a 5-meter ultrasonic level meter generally refers to the maximum distance of measuring the calm water surface is 5 meters, and the actual factory will do 6 meters. In the case of agitation in the container, the water surface is not calm, and the reflected signal will weaken to less than half of the normal signal.
Solution skills
Choose a larger range of ultrasonic level meter, if the actual range is 5 meters, it is necessary to use 10 meters or 15 meters of ultrasonic level meter to measure. If you do not change the ultrasonic level meter, and the liquid in the jar is non-viscous, you can also install a wave guide tube, and put the ultrasonic level meter probe in the wave guide tube to measure the height of the level meter, because the liquid level in the wave guide tube is basically stable. It is suggested to change the two-wire ultrasonic level meter into a four-wire one.
3. When there is foam on the surface of the liquid, the ultrasonic level meter will always show the search, or report the "lost wave" status.
Fault cause
The foam will significantly absorb ultrasonic waves, resulting in a very weak echo signal. Therefore, when more than 40-50% of the liquid surface is covered with foam, most of the signal emitted by the ultrasonic level meter will be absorbed, causing the level meter to receive no reflected signal. This does not have much to do with the thickness of the foam, but mainly with the area covered by the foam.
Solution skills
Install the wave guide tube, and put the ultrasonic level meter probe in the wave guide tube to measure the height of the level meter, because the foam in the wave guide tube will be reduced a lot. Or replace it with a radar level meter to measure, which can penetrate foam within 5 cm.
4. When there is electromagnetic interference on the scene, the data of the ultrasonic level meter will beat irregularly, or show no signal.
Fault cause
There will be many motors, frequency converters and welding in the industrial field, which will affect the measurement of ultrasonic level meters. Electromagnetic interference will outweigh the echo signal received by the probe.
Solution skills
The ultrasonic level meter is reliably grounded, and after grounding, some interference on the circuit board will be shielded through the ground wire. Note that this ground point must be grounded separately and cannot share the same ground point with other devices. At the same time, the power supply can not be the same power supply as the frequency converter and the motor, nor can it be directly generated from the power system. The installation location should be far away from the frequency converter, frequency conversion motor, high-power electric equipment. If it can not be far away, it is necessary to install a metal instrument box outside the level meter to isolate the shield, and the instrument box should also be grounded.
5. When the temperature in the on-site pool or jar is high, the ultrasonic level meter measurement is affected. When the water is close to the probe, it can be measured, and when the water is far from the probe, it can not be measured. When the water temperature is low, the ultrasonic level meter is normal, and on the contrary, it can not be measured normally.
Fault cause
Generally, the liquid medium will not produce steam and fog below 30-40 ° C, and it is easy to produce steam or fog beyond this temperature. The ultrasonic wave emitted by the ultrasonic level meter will attenuate once through the steam during the emission process, and then attenuate again when reflected back from the liquid level, resulting in a weak ultrasonic signal that eventually returns to the probe and therefore cannot be measured. In this environment, the probe of the ultrasonic level meter is easy to form water droplets, hindering the transmission and reception of the ultrasonic wave.
Solution skills
When selecting a larger range, the actual pot height is 3 meters, and an ultrasonic level meter of 6-9 meters should be selected. The size of the range of the ultrasonic level meter is related to the strength of its signal wave, and choosing a stronger signal can reduce the influence of steam or fog on the measurement. The probe should use a physically sealed housing of polytetrafluoroethylene or PVDF material, so that the probe emission surface is not easy to condense water. On the emission surface of other types of materials, water beads are generally easier to coagulate than the above two materials.
If you want to know more about the flow meter or flow meter selection, please consult the Aister flow meter manufacturer email: sales@aistermeter.com for help.
Fault cause
Ultrasonic level meter has a blind area, generally within 5 meters of the range, the blind area is 0.3-0.4 meters. The range within 10 meters is 0.4-0.5 meters. After entering the blind area, the ultrasound will appear arbitrary values and cannot work normally.
Solution skills
The height of the blind area should be considered when installing, and the distance between the probe and the highest water level must be greater than the blind area after installation.
2. The liquid fluctuation is relatively large when there is stirring in the field container, which will affect the measurement of the ultrasonic level meter. At this time, the instrument has no signal or the data fluctuates greatly.
Fault cause
The ultrasonic level meter said to measure a few meters away refers to the calm water surface. For example, a 5-meter ultrasonic level meter generally refers to the maximum distance of measuring the calm water surface is 5 meters, and the actual factory will do 6 meters. In the case of agitation in the container, the water surface is not calm, and the reflected signal will weaken to less than half of the normal signal.
Solution skills
Choose a larger range of ultrasonic level meter, if the actual range is 5 meters, it is necessary to use 10 meters or 15 meters of ultrasonic level meter to measure. If you do not change the ultrasonic level meter, and the liquid in the jar is non-viscous, you can also install a wave guide tube, and put the ultrasonic level meter probe in the wave guide tube to measure the height of the level meter, because the liquid level in the wave guide tube is basically stable. It is suggested to change the two-wire ultrasonic level meter into a four-wire one.
3. When there is foam on the surface of the liquid, the ultrasonic level meter will always show the search, or report the "lost wave" status.
Fault cause
The foam will significantly absorb ultrasonic waves, resulting in a very weak echo signal. Therefore, when more than 40-50% of the liquid surface is covered with foam, most of the signal emitted by the ultrasonic level meter will be absorbed, causing the level meter to receive no reflected signal. This does not have much to do with the thickness of the foam, but mainly with the area covered by the foam.
Solution skills
Install the wave guide tube, and put the ultrasonic level meter probe in the wave guide tube to measure the height of the level meter, because the foam in the wave guide tube will be reduced a lot. Or replace it with a radar level meter to measure, which can penetrate foam within 5 cm.
4. When there is electromagnetic interference on the scene, the data of the ultrasonic level meter will beat irregularly, or show no signal.
Fault cause
There will be many motors, frequency converters and welding in the industrial field, which will affect the measurement of ultrasonic level meters. Electromagnetic interference will outweigh the echo signal received by the probe.
Solution skills
The ultrasonic level meter is reliably grounded, and after grounding, some interference on the circuit board will be shielded through the ground wire. Note that this ground point must be grounded separately and cannot share the same ground point with other devices. At the same time, the power supply can not be the same power supply as the frequency converter and the motor, nor can it be directly generated from the power system. The installation location should be far away from the frequency converter, frequency conversion motor, high-power electric equipment. If it can not be far away, it is necessary to install a metal instrument box outside the level meter to isolate the shield, and the instrument box should also be grounded.
5. When the temperature in the on-site pool or jar is high, the ultrasonic level meter measurement is affected. When the water is close to the probe, it can be measured, and when the water is far from the probe, it can not be measured. When the water temperature is low, the ultrasonic level meter is normal, and on the contrary, it can not be measured normally.
Fault cause
Generally, the liquid medium will not produce steam and fog below 30-40 ° C, and it is easy to produce steam or fog beyond this temperature. The ultrasonic wave emitted by the ultrasonic level meter will attenuate once through the steam during the emission process, and then attenuate again when reflected back from the liquid level, resulting in a weak ultrasonic signal that eventually returns to the probe and therefore cannot be measured. In this environment, the probe of the ultrasonic level meter is easy to form water droplets, hindering the transmission and reception of the ultrasonic wave.
Solution skills
When selecting a larger range, the actual pot height is 3 meters, and an ultrasonic level meter of 6-9 meters should be selected. The size of the range of the ultrasonic level meter is related to the strength of its signal wave, and choosing a stronger signal can reduce the influence of steam or fog on the measurement. The probe should use a physically sealed housing of polytetrafluoroethylene or PVDF material, so that the probe emission surface is not easy to condense water. On the emission surface of other types of materials, water beads are generally easier to coagulate than the above two materials.
If you want to know more about the flow meter or flow meter selection, please consult the Aister flow meter manufacturer email: sales@aistermeter.com for help.
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