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The first one is that there is stirring in the field container, and the fluid fluctuation is relatively large, which affects the measurement of the ultrasonic level gauge.
Symptoms: No signal or data fluctuations.
Reason: The ultrasonic level gauge says a distance of several meters, which means calm water. For example, an ultrasonic level gauge with a range of 5 meters generally means that the maximum distance for measuring calm water is 5 meters, and the actual factory will be 6 meters. When there is stirring in the container, the water surface is not calm and the reflected signal will be reduced to less than half of the normal signal.
Solution: 1. Choose a more large-scale ultrasonic liquid level gauge. If the actual range is 5 meters, use an ultrasonic liquid level meter of 10 meters or 15 meters to measure.
2. If you do not change the ultrasonic level gauge and the liquid in the tank is not sticky, you can also install the waveguide. Put the ultrasonic level gauge probe in the waveguide to measure the height of the level gauge, because the liquid level in the waveguide is basically stable.
3. It is recommended to change the two-wire ultrasonic level gauge to four-wire.
Second: There is foam on the liquid surface.
Symptoms: Ultrasonic level gauges are constantly searching, or show "wave drop" status.
Cause: The foam can absorb ultrasound significantly, resulting in very weak echo signals. Therefore, when more than 40-50% of the surface of the liquid is covered with foam, the signal emitted by the ultrasonic level gauge will absorb most of the signal, causing the level gauge to receive no reflected signal. This has nothing to do with the thickness of the foam, mainly related to the area covered by the foam.
Solution: 1. Install the waveguide, and place the ultrasonic level probe in the waveguide to measure the height of the level gauge, because the foam in the waveguide will be reduced much.
2. Replace it with a radar level gauge. The radar level gauge can penetrate the foam within 5 centimeters.
The third type; high temperature in the water tank or tank on site, which affects the ultrasonic level gauge measurement.
Symptom: When the water surface is near the probe, it can be measured. The water surface cannot be measured far from the probe. When the water temperature is low, ultrasonic level gauge measurement is normal, and if the water temperature is high, the ultrasonic level gauge cannot measure it.
Reason: The liquid medium usually does not generate steam and fog below 30-40°C. Above this temperature, steam or mist will be easily generated. Ultrasonic waves emitted by the ultrasonic level gauge will attenuate once during the launch and reflect from the liquid surface. When it is attenuated once again, the ultrasonic signal finally returned to the probe is very weak, so it cannot be measured. And in this environment, the ultrasonic liquid level meter probe is easy to get water droplets, water droplets will hinder the transmission and reception of ultrasonic waves.
Solution: 1. To increase the range, the actual height of the tank is 3 meters, to choose 6 meters to 9 meters ultrasonic level gauge. The effect of steam or mist on the measurement can be reduced or reduced.
2. The probe should be made of PTFE or PVDF to make it physically sealed. Such probes will not condense water droplets on the emitting surface. The emission surface of other materials, the water droplets are easier to condense.
Fourth: There is electromagnetic interference in the scene.
Symptoms: Ultrasonic liquid level meter data irregularly beats, or simply shows no signal.
Cause: Many electric motors, inverters, and electric welding on the industrial site will affect the ultrasonic level gauge measurement. Electromagnetic interference can exceed the echo signal received by the probe.
Solution: 1. Ultrasonic liquid level meter must be grounded reliably. After grounding, some interference on the circuit board will run off through the ground wire. And this grounding is to be grounded alone and cannot share a ground with other equipment.
2. The power supply can not be the same power supply as the inverter or motor, nor can it be directly powered from the power system power supply.
3. The installation site should be far away from the inverter, variable frequency motor, and high-power electrical equipment. If it can not be far away, it is necessary to install a metal instrument box on the outside of the gauge to isolate the shield. This instrument box should also be grounded.
Fifth: Enter the blind spot
Symptom: Full-scale or arbitrary data appears.
Reasons: Ultrasonic level gauges have blind areas, usually within 5 meters range, the blind area is 0.3-0.4 meters. The measurement range is 0.4-0.5 meters within 10 meters. After entering the blind spot, the ultrasound will appear to have an arbitrary value and will not work properly.
Solution: 1. The height of the blind spot should be considered when installing. The distance between the probe and the highest water level must be greater than the blind spot after installation.
The above reasons may cause the ultrasonic level gauge to work abnormally. Therefore, when purchasing the ultrasonic level gauge, it is necessary to put on-site working conditions and experienced customer service to help you select the type and recommend how to install it. Ensure that the ultrasonic level gauge works properly.
Because ultrasonic waves emitted by the ultrasonic level gauge are invisible to the human eye, the abnormal working conditions at the site have occurred. In addition to the failure of the level gauge itself, we have summarized some of them and told you:
March 24, 2023