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What are the reasons for the abnormal working of the ultrasonic level gauge

by:Sure     2021-08-24
The first type: there is stirring in the on-site container, and the liquid fluctuates greatly, which affects the measurement of the ultrasonic level gauge. Trouble phenomenon: The ultrasonic level gauge has no signal or the data fluctuates badly. Reason: Ultrasonic level gauges talk about measuring distances of a few meters, all referring to calm water. For example, an ultrasonic level gauge with a range of 5 meters generally means that the maximum distance to measure a calm water surface is 5 meters, but the actual factory will achieve 6 meters. In the case of 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 larger-range ultrasonic level gauge. If the actual range is 5 meters, use a 10-meter or 15-meter ultrasonic level gauge to measure. 2. If you do not change the ultrasonic level gauge and the liquid in the tank is non-viscous, you can also install a stilling wave tube. Put the ultrasonic level gauge probe in the stilling wave tube to measure the height of the level gauge, because the liquid level in the stilling wave tube is basically stable. 3. It is recommended to change the two-wire ultrasonic level gauge to a four-wire system. The second type: there is foam on the surface of the liquid. Trouble phenomenon: The ultrasonic level gauge is always searching, or it displays the 'lost wave' status. Reason: The foam will obviously absorb ultrasonic waves, resulting in very weak echo signals. Therefore, when more than 40-50% of the liquid surface is covered with foam, most of the signal emitted by the ultrasonic level gauge will be absorbed, causing the level gauge to fail to receive the reflected signal. This has nothing to do with the thickness of the foam, it is mainly related to the area covered by the foam. Solution: 1. Install the still wave tube, put the ultrasonic level gauge probe in the still wave tube to measure the height of the level gauge, because the foam in the still wave tube will decrease a lot. 2. Replace it with a radar level gauge for measurement. The radar level gauge can penetrate bubbles within 5 cm. The third type; the high temperature in the on-site pool or tank affects the measurement of the ultrasonic level gauge. Trouble phenomenon: It can be measured when the water surface is close to the probe, but cannot be measured when the water surface is far away from the probe. When the water temperature is low, the ultrasonic level gauge measures normally, but the ultrasonic level gauge cannot measure when the water temperature is high. Reason: The liquid medium generally does not produce steam or mist when the temperature is below 30-40℃. When the temperature exceeds this temperature, steam or mist is easy to be generated. The ultrasonic wave emitted by the ultrasonic level gauge will attenuate once through the steam during the transmission process and reflect back from the liquid surface. Attenuation is required once again, which results in a weak ultrasonic signal returning to the probe, so it cannot be measured. Moreover, in this environment, the ultrasonic level gauge probe is prone to water droplets, which will hinder the transmission and reception of ultrasonic waves. Solution: 1. To increase the range, the actual tank height is 3 meters, and an ultrasonic level gauge of 6-9 meters should be selected. It can reduce or weaken the influence of steam or mist on the measurement. 2. The probe should be made of polytetrafluoroethylene or PVDF and made into a physically sealed type, so that water droplets are not easy to condense on the emitting surface of such a probe. On the emitting surface of other materials, water drops are easier to condense. Fourth: There is electromagnetic interference on site. Trouble phenomenon: The data of the ultrasonic level gauge fluctuates irregularly, or simply shows no signal. Reason: There are many electric motors, frequency converters and electric welding in the industrial field, which will affect the measurement of ultrasonic level gauge. Electromagnetic interference can exceed the echo signal received by the probe. Solution: 1. The ultrasonic level gauge must be grounded reliably. After grounding, some interference on the circuit board will run away through the ground wire. And this ground is to be grounded separately, it cannot share the same ground with other equipment. 2. The power supply cannot be the same power supply as the frequency converter and motor, nor can it be directly drawn from the power supply of the power system. 3. The installation site should be far away from frequency converters, frequency conversion motors, and high-power electric equipment. If it cannot be far away, a metal instrument box must be installed outside the level gauge to isolate and shield it, and this instrument box must also be grounded. The fifth type: entering the blind zone. Trouble phenomenon: full scale or arbitrary data appears. Reason: Ultrasonic level gauges have blind areas, generally within 5 meters of 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 zone, the ultrasound will show arbitrary values u200bu200band cannot work normally. Solution: 1. When installing, consider the height of the blind zone. After installation, the distance between the probe and the highest water level must be greater than the blind zone. Huahai Measurement and Control Ultrasonic Level Gauge Product Features: 1. The circuit design selects high-quality power modules from the power supply part, and the components choose imported high-stable and reliable components, which can completely replace the same type of imported foreign instruments. 2. The patented sonic intelligent technology software can perform intelligent echo analysis without any debugging and other special steps. This technology has the functions of dynamic thinking and dynamic analysis. 3. High precision, liquid level precision reaches 0.25%, and it can resist various interference waves. 4. It is a non-contact instrument, which does not directly contact the liquid, so the failure rate is low. The instrument provides a variety of installation methods, and users can calibrate the instrument through this manual. 5. All input and output wires of the instrument have the protection function of lightning protection and short circuit protection.
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