Ultrasonic level meter troubleshooting
Ultrasonic level meter, which is familiar to everyone, can be widely used for various liquids (such as sewage treatment, corrosive liquid measurement) and solid material height measurement due to non-contact measurement.
Here is a brief introduction of dealing with ultrasonic level meter problems.
First: entering the blind zone
Symptom: Full scale or arbitrary data.
Reason: The ultrasonic level gauge has a blind zone, generally within a range of 5 meters, the blind zone is 0.3-0.4 meters. The range within 10 meters is 0.4-0.5 meters. After entering the blind zone, the ultrasonic wave will have any value and it will not work properly.
Solution: before installation, consider the height of the blind zone. After installation, the distance between the probe and the high water level must be greater than the blind zone.
Second: Stirring effect
There is agitation inside the container, and the liquid fluctuation is relatively large, which affects the measurement of the ultrasonic level meter.
Symptom: No signal or data fluctuations.
Reason: The measurement of the distance of a few meters by the ultrasonic level gauge refers to the calm water surface. For example, 5m ultrasonic level meter range generally means that the measured distance of the water surface max is 5 meters, and the actual factory will be 6 meters. In the case of agitation 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 Tip: Use a larger range ultrasonic level meter, If the actual range is 5 meters, measure with a 10 meter or 15 meter ultrasonic level meter. If the ultrasonic level meter is not changed and the liquid in the tank is not sticky, a wave guide can be installed, and the ultrasonic level meter probe is placed in the wave guide to measure the height of the liquid level gauge, because the liquid level in the wave guide is basically stable. It is recommended to change the two-wire ultrasonic level gauge to a four-wire system.
Third: Liquid surface has foam
Symptom: The ultrasonic level meter is always searching or displaying the“lost wave” status.
Reason: The foam will absorb the ultrasonic waves significantly, resulting in a very weak echo signal. Therefore, when 40-50% of the surface of the liquid surface covers the foam, the signal emitted by the ultrasonic level meter will be absorbed most, causing the level meter to receive no reflected signal. This has little to do with the thickness of the foam, mainly related to the area covered by the foam.
Solution: Install the wave guide, and place the ultrasonic level meter probe in the wave guide to measure the height of the level gauge, because the foam inside the wave guide will be much reduced. Or replace it with a radar level meter to measure, the radar level meter can penetrate the foam within 5 cm.
Fourth: electromagnetic interference
Symptom: The ultrasonic level meter data is not beating regularly, or it simply shows no signal.
Reason: There will be many motors, frequency converter and electric welding in the industrial field that will affect the measurement of the ultrasonic level meter, Electromagnetic interference will exceed the echo signal received by the probe.
Solution: The ultrasonic level meter must be grounded reliably. After grounding, some interference on the board will run off the ground. Moreover, this grounding is to be grounded separately and cannot share a ground with other equipment. The power supply cannot be connected to the same power source as the frequency converter or the motor, nor can it be directly powered from the power system power supply. Keep away from frequency converter, variable frequency motors, and high-power electric equipment. If you can't stay away, install a metal instrument box outside the level gauge to isolate the shield. This instrument box should also be grounded.
Fifth: temperature effect
The temperature in the on-site pool or tank is high, which affects the measurement of the ultrasonic level meter.
Symptom: When the water surface is close to the probe, it can be measured. The water surface is not measured far from the probe. When the water temperature is low, the ultrasonic level meter is measured normally, and the water temperature is high and the ultrasonic level meter is not measured.
Reason: the liquid medium generally does not generate steam and mist below 30-40°C. Above this temperature, steam or mist is easily generated. The ultrasonic wave emitted by the ultrasonic level meter will attenuate once through the steam during the emission process, and reflect from the liquid surface. When it comes back, it has to be attenuated again, causing the ultrasonic signal back to the probe to be weak, so it can't be measured. Moreover, in this environment, the ultrasonic level meter probe is prone to water droplets, which prevent the transmission and reception of ultrasonic waves.
Solution: To increase the range, the actual tank height is 3 meters, and you should choose an ultrasonic level meter of 6 meters to 9 meters. The effect of steam or mist on the measurement can be reduced or reduced. The probe should be made of Teflon or PVDF to make it physically sealed. Such a probe surface does not easily condense water droplets. On the emitting surface of other materials, water droplets are more likely to condense.