Because all kinds of ultrasonic flowmeters can be installed outside the pipe, non-contact flow measurement, the cost of the instrument is basically independent of the size of the pipe to be tested, while other types of flowmeters increase with the increase in caliber, so the cost is increased. The flowmeter is superior to the other functions of the same type of flowmeter. It is considered to be a good large-diameter flow measuring instrument. The Doppler ultrasonic flowmeter can measure the flow of two-phase medium, so it can be used for the measurement of dirty sewage such as sewers and sewage. In power plants, the use of portable ultrasonic flowmeters to measure large pipe diameters such as turbine water inflow and turbine circulating water is much more convenient than in the past. Ultrasonic flow juice can also be used for gas measurement. Pipe diameters range from 2cm to 5m, from a few meters wide open channels, culverts to 500m wide rivers.
In addition, the accuracy of the flow measurement of the ultrasonic measuring instrument is almost independent of the temperature, pressure, viscosity, density and other parameters of the measured fluid, and can be made into non-contact and portable measuring instruments, so it can solve the problem that other types of instruments are difficult to measure. Flow measurement problems for corrosive, non-conductive, radioactive, and flammable and explosive media. In addition, in view of the non-contact measurement characteristics, coupled with reasonable electronic circuits, one instrument can adapt to a variety of pipe diameter measurements and a variety of flow range measurements. The adaptability of ultrasonic flowmeters is also unmatched by other instruments. Ultrasonic flowmeters have some of the above advantages, so it has received more and more attention and has been developed into a series of products and generalization. It has been made into standard, high-temperature, explosion-proof and wet instruments of different channels to adapt to different media. Flow measurement for occasions and different pipeline conditions.
Measuring principle of electromagnetic flowmeter
The principle of electromagnetic flowmeter measurement is based on Faraday's law of electromagnetic induction. The measuring tube of the flow meter is a non-magnetic alloy short tube lined with an insulating material. The two electrodes are fixed to the measuring tube through the tube wall in the tube diameter direction. The electrode tip is substantially flush with the inner surface of the liner. When the exciting coil is excited by the bidirectional square wave pulse, a working magnetic field having a magnetic flux density B is generated in a direction perpendicular to the axis of the measuring tube. At this time, if the fluid having a certain conductivity passes through the measuring tube, the cutting magnetic line induces the electromotive force E. The electromotive force E is proportional to the product of the magnetic flux density B, the inner diameter D of the measuring tube and the average velocity V. The electromotive force E (flow signal) is detected by the electrode and sent to the converter through the cable. After the converter amplifies the flow signal, it can display the fluid flow, and can output signals such as pulse and analog current for flow control and regulation.
Ultrasonic flowmeter classification
Plug-in ultrasonic flowmeter: can be installed and maintained without interruption. Ceramic sensors are used for non-stop production installation using dedicated drilling equipment. Generally for mono measurement, in order to improve measurement accuracy, three channels can be selected.
Pipe-type ultrasonic flowmeter: the pipeline installation needs to be cut, but the subsequent maintenance can be stopped. Mono or 3-channel sensors are available.
External clip-on ultrasonic flowmeter: capable of performing fixed and mobile measurements. It is installed with a special coupling agent (silicone rubber cured at room temperature or high-temperature long-chain polymer grease) and does not damage the pipeline during installation.
Portable Ultrasonic Flowmeter: Portable, built-in rechargeable lithium battery, suitable for mobile measurement, with magnetic sensor.
1, non-contact measurement method, small size, easy to carry
2, suitable for on-site measurement of various sizes of pipe sound guiding media
3, built-in nickel-metal hydride rechargeable battery working time of more than 20 hours
4, user interface is flexible, easy to use
5, intelligent on-site printing function to ensure the integrity of the flow data
6, equipped with an integrated aluminum alloy protective box, can be used in harsh outdoor environments
Hand-held ultrasonic flowmeter: small size, light weight, built-in rechargeable lithium battery, hand-held, with magnetic sensor.
Explosion-proof ultrasonic flowmeter: used for explosive liquid flow measurement, it is explosion-proof and intrinsically safe. That is, the converter is explosion-proof and the sensor is intrinsically safe.