As a standard meter, portable ultrasonic flowmeters often have errors when compared with online electromagnetic flowmeters. Some errors are even more difficult to accept. The technical service engineers of Shanghai Senyi Intelligent Instrument Co., Ltd. analyze according to years of testing and field experience. The cause of the error, such as the environment of the measurement, the condition of the measuring pipe, the performance of the instrument itself, the specification of the operation of the instrument, and so on.
Ultrasonic flowmeter has the advantages of reasonable price, simple installation, no fragile parts, convenient maintenance and verification. Among them, the portable ultrasonic flowmeter has a wide measuring range. Although its accuracy is inferior to that of some electromagnetic flowmeters, its accuracy is very high under certain working conditions, which can reach two thousandths or more. It is a rare online calibration of flowmeters. Auxiliary tools. At present, on-site calibration in the water, water conservancy bureau, sewage treatment, petrochemical, electric power and other industries is inseparable from the portable ultrasonic flowmeter.
Due to the measurement of the ultrasonic flowmeter, its measurement environment and field conditions directly affect its accuracy. How can we improve the accuracy of the portable ultrasonic flowmeter?
First of all, we must choose a portable ultrasonic flowmeter with superior performance. Secondly, we must operate the ultrasonic flowmeter strictly according to the operating specifications. How to choose it, we will not decompose it in detail here. After all, its performance has a certain relationship with the price. The actual experience of the engineers of Instrument Co., Ltd., to talk about how to improve the accuracy of the existing ultrasonic flowmeter.
First: choose the right measurement point
The measuring point is the position of the flow sensor used to install the ultrasonic flowmeter. Due to the different measuring conditions and environment, there are many measuring points. How to choose? The first is to have horizontal pipelines and try not to test them in vertical pipelines. If you can only test in vertical pipelines, you should try to choose the direction of water flow from bottom to top, and the measurement points should meet the straight pipe sections of the first 10 times. , 5 times the diameter of the straight pipe section, away from the pump port, valves, reducers, bends, etc.
Second: the setting of parameters
Before the measurement, the portable ultrasonic flowmeter should input the pipe material, wall thickness, fluid type, medium temperature (with temperature compensation table) and installation method of the site measurement point into the table in turn, during on-site training or testing. I often hear the field engineer say that the outer diameter is about 300MM, the wall thickness is about 6MM, it may be the material of cast iron, etc. If so, I can only say that there should be fluid flow in the pipeline, and the specifics can only be approximated. Therefore, it is necessary to strictly treat the pipe material, wall thickness, fluid type, medium temperature (with temperature compensation table), installation method, etc., can be measured on site, on-site test, do not believe probably, believe in the data measured by yourself, Generally, the outer diameter of the pipe can be directly tested with a tape measure. The wall thickness can be measured with a thickness gauge. The temperature of the water can be tested with a surface thermometer. When measuring these data, try to measure each set of data 5 times, then take The average value, especially the wall thickness measurement, must be selected a few more points. After all, the level of domestic pipeline processing is limited.
Third: How to install the sensor
There is no fixed statement, but the number of times the site is asked is the most. The diameter of the DN is suitable for the installation method. This can only be determined according to the usual experience. In general, the sound layer is directly used (the domestic method is called Z method). ) is absolutely correct. In the actual test process, in order to simplify the measurement, choose 2 sound layer test (domestic called V method), and the sensor is easy to install on the same side.
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