I. Overview Ultrasonic level gauge is a non-contact liquid measuring instrument. It can be used to measure liquid level and flow in various vessel pipelines. It can also be used in the measurement of water levels in drains, reservoirs, rivers and lakes. It is especially suitable for sewage and corrosive applications such as urban drainage pumps. The water level of the station before and after the trash rack, and the water level in the water treatment plant are measured. Due to the strong corrosiveness of urban sewage and water purification agent polymeric aluminum oxide, if a contact pressure water level gauge is used, the sensor must be inserted into the sewage, so that the probe will soon corrode and affect the normal measurement. In addition, the ultrasonic liquid level gauge has high measurement accuracy, easy installation and maintenance, and can simultaneously measure the characteristics of water level, water level difference, and amount of materials used. Therefore, more and more widely used applications.
Second, the working principle of ultrasonic Ultrasonic level gauge probe installed above the liquid to be measured, the probe is stimulated by the electricity, through the air to the liquid below the ultrasonic emission, the ultrasonic will be reflected by the liquid, the echo is received and monitored by the probe, It is converted to electrical signals. The time required between ultrasonic transmission and reception is proportional to the distance between the probe and the liquid surface. For example, the distance D is determined by the acoustic wave velocity C and the transmission time t as shown in formula (1):
D=C*t/2(1)
Under normal circumstances, the propagation speed of sound waves in the air is 340m/s. If the transmission time is toms, the corresponding transmission distance is 3.4m, so the pitch is 1.7m. The ultrasonic level gauge actually measures the height of the liquid level change, and can be converted into the actual liquid depth by setting the ultrasonic level gauge in advance.
Third, the application of ultrasonic level gauge FMU series ultrasonic level gauge exquisite design, easy installation and use, high precision, durability, good anti-interference properties, can be used alone, can also be used in conjunction with computer PLC. The commonly used models are type 860 (measurement of sealed container level), type 861 (measurement level and flow rate) and type 862 (using two probes, can measure two different liquid level at the same time, that can measure the level difference). FMU series ultrasonic level gauge consists of two parts: instrument and probe, which can be applied to various occasions.
1. Level Gauge Meter Ultrasonic level gauge The meter panel has digital display and parameter setting. Touch the model button; the lower part of the meter has service group connection terminals, which are connected to 220V power supply, relay and sensor probes. The meter part of the level gauge should generally be mounted vertically at an appropriate height on the wall. It must be securely mounted to allow the user to observe and perform setup operations.
2 Level Gauge Probes and Mounting Level Gauge Probes (Sensors) There are five models that can be used to measure the depth of a liquid, and can also be used to measure the solid height. In order to ensure accurate measurement, the probe has the function of automatically clearing the snow and ice covered by its surface. When installing, outdoor probes should be covered to avoid direct sunlight and rain, and they should be installed vertically on the support. The distance from the probe to the liquid surface is determined by the maximum depth of liquid fluctuations and the probe's range. If you are measuring liquids that have other impurities, such as dirty water, you should install wire mesh surrounding the probe to isolate floating impurities outside the correct measurement range of the probe. Barbed wire mesh can be determined by the size of the smallest impurity that actually needs to be isolated. Two layers of wire mesh can also be used. The outer layer is larger and the inner layer is smaller. It is best to use stainless steel wire mesh screen to avoid excessive corrosion, affecting the normal operation of the level gauge. Wells are generally about 1 meter in diameter.
The probe comes with a signal cable with a length of one metre. However, the monitoring point is generally far away from the level meter of the level gauge or the control room of the computer. It is necessary to add an extension cable. Because the shielded cable price is too high, according to the requirements in the manual And market research, choose shielded cable with larger cross-sectional area as extension cable, the maximum resistance of each core is 6 ohms, and the maximum length is not more than 300 meters. It is better to use better-quality double shielded cable in Taiwan, and the grounding is good, otherwise it will affect Measure performance. For the case of poor cable laying, a wireless sampling module can be used to connect with the level gauge probe, and the wireless sampling module is also used for receiving in the control room, which is more flexible and convenient. The maximum distance is about 500 meters.
3. Setting of ultrasonic level gauge According to the working principle of the ultrasonic level gauge, the time taken by the probe to emit and receive the ultrasonic wave is calculated and measured as the distance between the probe and the liquid surface. In order to display the height of the liquid level, it is necessary to enter Conversion, so make the necessary parameter settings for the level gauge. The parameters such as the liquid level height, the maximum liquid level, and the minimum liquid level during initialization are set, and the linearized treatment makes it possible to dynamically measure the depth of the changed liquid. In addition, the ultrasonic liquid level gauge can also be connected to the industrial control computer through the network. In order to make the data displayed in the computer configuration interface consistent with the data displayed by the ultrasonic level gauge, some parameters must be properly corrected and adjusted. The basic settings are as follows:
1) Set the unit (meters or feet), the default setting (meters);
2) Set the measured object mode: 1 fluid, 2 water level change, 3 round seal, 4 solid, 5 conveyor belt;
3) Set the null value (meter);
4) Set full value (m);
5) Set the sensor (probe) model;
6) Set up relays to connect external alarm limit switches and other equipment;
After the ultrasonic liquid level meter is set up, it should also be adjusted and adjusted according to the actual liquid level at the time to ensure the accuracy of the liquid level meter and the measurement data. If connected to a computer system, the liquid level display on the computer should also be properly adjusted to equal the displayed value on the level gauge. Finally, once the ultrasonic level gauge is set up, it should not be tampered with, so as not to affect normal operation.
IV. Application of Level Gauge Because ultrasonic level gauge has many characteristics, especially non-contact measurement, it can be widely used in reactors, reactor tanks, etc. in chemical companies and various pipelines and drains that need to calculate flow. At present, it is widely used in water level measurement in rivers, rivers, lakes and seas. It not only measures accurately, but also continuously measures and records hydrological data in detail. It also avoids the difficulty and danger of seeing the water level scale during the rainstorm and during the flood season. Greatly reduced the labor intensity of hydrographers and improved the scientificity of monitoring.
Through the application research of FMU series ultrasonic level gauges, using its advantages of non-contact measurement, it is practically used in the remote data collection and monitoring systems of drainage pumps stations in cities and large schools, and blocks the pump stations in the cities and schools. The automatic monitoring of the water level in front of the grid and behind the grid can make a major contribution to the urban and school sewage and purification environment and achieve good social and economic benefits. In addition, FMU series ultrasonic level gauges are stable, reliable, and can be applied.
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The main function of the edge banding is to seal the cross-section of the board, so as to avoid the damage of the board and the adverse factors (mainly moisture) in the process of use and prevent the formaldehyde inside the board from volatilizing, and at the same time achieve the effect of beautiful decoration.
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The precise edge sealing design of the board can prevent water or other liquids from entering the board, avoiding the expansion, deformation and breeding of bacteria on the desktop, thereby prolonging the service life of the office furniture, and the office furniture after the edge sealing treatment is also more expensive in terms of cleaning easy.
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