Non contact liquid level measurement technology
users in the process industry usually do not need high-precision liquid level measurement. They only need the early warning when the liquid is limited by the oil source flow and reaches the warning line, and the alarm when the liquid overflows the container or the container is empty. Therefore, simple mechanical detection devices are still widely used, and the application is good. Generally, there is a full use record on site and reliable service is provided. However, this task is more challenging when the liquid level detection needs to be carried out in the separator or under harsh process conditions, or when the calibration data needs to be transferred to a higher-level liquid level container management system. These applications reflect the general trend and current choice of high-precision equipment with simple operation. Which technology is suitable depends on the measurement scheme and medium. We have seen a growing demand for radar sensor based solutions
"although in enraf, we have made the performance, accuracy and reliability of servo technology perfect, we see the greater potential of radar measurement. We are developing new software to increase the reliability of the equipment, which will also expand its application range in more occasions. Our goal is to achieve the optimal application of tank capacity through liquid level measurement," said Wilfried landerer of enraf, "Even in the future, for radar technology, we will not see the application process of 'universal' devices. In other words, the mechanical and physical environment will determine which measurement method is the best."
the system should be simplified as much as possible
users need as simple products as possible. Product operators no longer need time to check various probes in the system. G ü nter pinkowski of KROHNE company pointed out: "users want to install a meter in the container, use it to detect some relatively simple problems, and hope that the meter works without errors." The market demand for spring compensator is to use this linear relationship to adjust the deformation through the involute wheel, so as to achieve a constant output tension, which requires simple steps, convenient operation and long-term free maintenance services. To meet these needs, KROHNE is focusing on improving the shortcomings of current radar liquid level detectors that users often complain about, that is, simplifying operation and making them suitable for special applications. KROHNE's latest generation of FMCW detectors can transmit clearer signals and more information in containers. It can distinguish weak measurement signals from strong reflection signals. This technology is also applied to the new Optiflex, which is a device for receiving radar reflection signals. "We see that measurement technology that brings real benefits to users will become increasingly popular. This method is suitable for universal application and is simple and reliable."
Rainer waltersbacher of Vega grieshaber explained that undirected microwave (radar) and guided microwave (TDR) can meet these needs well. In addition to pure technological development, the company will also focus on equipment handling and operation. Vega's professional application antennas include parabolic antennas designed for liquids with poor reflection performance. The application temperature range of the parabolic antenna is - 40 ℃ ~ + 200 ℃; The pressure range is: from vacuum to 3bar
Andrew Blazey, marketing director of Siemens liquid level measurement products in Peterborough, Canada, also believes that radar is the key technology. "Contactless liquid level detection is the most potential product for continuous liquid level detection at present. At Siemens, we will focus on developing this technology. Compared with other methods, this technology shows the largest growth rate and technical advantages." In addition to the ultrasonic SITRANS probe Lu, the two-wire radar meter will be launched this summer
two wire measuring device with digital interface
Emerson Process Management also embarks on radar technology, which is applied not only to tank measurement, but also to process applications. Jens weselmann, marketing manager of radar liquid level products, said, "the biggest application field of compact two-wire measuring instruments that provide a digital data interface is process engineering. The current product series provides good performance for many applications. However, Emerson Process management expects to cover the entire process technology market with their products."
rosemount5400 liquid level gauge has recently entered the market. The two-wire measuring device has two antennas and has many similar features with rsemount, including a movable cover and a rotary display. The equipment adopts Saab Rosemount's patent, dual port technology and cycle technology, which draws on the high-precision Rex product series. Dual port reference separation send/receive modules, which make the target reflection and interference signals easy to identify. The circular model technology ensures that 5400 can filter out the multiple reflection signals reflected from the container wall before software capture
application potential in small tanks
in many large and small storage tank areas, buffers and feeders have no liquid level at all 3 Equip the detection device after installation and commissioning
endress+hause's liquicap t product is designed to fill this gap. The product has a two axis capacitance probe, which can be used for continuous measurement of conductive liquids (30 μ S/cm or more). Its measuring range is 150 ~ 2500mm, and its processable temperature range is - 40 ~ ＋ 100 ℃. The probe length is preset in advance according to the special order during manufacturing, and the user's requirements cannot be considered during installation, so as to calibrate the probe. The Development Department of e+h will devote itself to research in two fields in 2005. Stefan Rejda, manager of the liquid level measurement Marketing Department of e+h company, shared his future plans with us. He told us that the company would carry out technological innovation and expand the application boundary of ultrasonic non-contact technology. I also want to add some new technical features to the limit switch of the vibrating container. Including sensor geometry, efficient process pressure and Namur interface. All these features will significantly increase the range of sensor applications
for non-traditional solutions, extreme conditions and media properties need to be considered. Pepperl+fuchs developed pulscon LTC products. According to Martin holdefer, the company believes that the pulscon LTC guided wave meter and the new luc-m, which will be launched in the second quarter, will provide great potential for the current product range. The new two-wire pulsocn LTC uses guided microwave based on the principle of TDR (time domain reflectometer). The pulse is guided by the guide rod or cable and will not be affected by the surface movement or the overlapping layer of gas and dust. At the same time, the coaxial probe can also brake, record and obtain an average value. An impact tester can provide reliable results, even when the medium is at a very low DK value. However, there is an alternative problem of conduction time. Mr. Walter Hein of turch pointed out the usefulness of direct analytical level detection: they believe that this technology will continue to have great potential in the future. The focus will be on continuous measurements, rather than pseudo analog measurements based on the sequential arrangement of spring contacts. Magnetic sensors, which have proved their effectiveness for a long time, provide a feasible solution. He believes that the challenge in the future is to integrate temperature sensors and their high temperature resistance
so far, there is still no universally applicable liquid level sensor, and the difference is mainly in terms of price and performance. High technology at any price is not always the right solution. Generally, high-precision liquid level measuring devices are not a problem. The biggest difficulty is under what conditions the sensor placed in the container is in, whether there is foam or under extreme temperature or pressure. Manufacturers are paying attention to preventing external influences from producing wrong measurement results
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