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Industry Information
Ultrasonic flowmeter measurement accuracy is hardly affected by media temperature and pressure parameters
2012-3-30 9:51:12

,就是利用超声波发射接收的原理,测非接触的测量液体深度。 The ultrasonic level gauge uses the principle of ultrasonic transmission and reception to measure the non-contact measurement of liquid depth. The propagation speed of the ultrasonic wave is relatively constant at a certain temperature. If the speed is known, the distance from the ultrasonic probe to the liquid surface can be calculated as long as the transmission and reception time of the ultrasonic wave is calculated. The depth of the tank or the tank is constant. Calculate the distance from the liquid surface to the probe, and then calculate the distance from the liquid surface to the bottom of the tank or tank, which is the depth of the liquid. Its advantage is non-contact measurement, which is relatively hygienic and can detect highly corrosive media. The disadvantage is that the requirements for the generation and reception of ultrasonic waves are high on the environment. In the case of harsh environments, the ultrasonic level gauge is not very suitable. With the increasing scarcity of water resources, the management and use of water resources by relevant departments are becoming more and more strict. At the same time, enterprises also urgently need to reduce the operating cost of the equipment to improve product competitiveness. In petroleum refining and chemical enterprises, how to ensure the effective measurement of large-diameter pipelines, especially those cast-iron pipelines that are buried deep in the ground and subjected to long-term oil pollution, to ensure accurate cost accounting Assessment has always been a difficult problem that disturbs the accuracy of measurement and the stable operation of the device. In response to this problem, two metering solutions are introduced:

它具有不接触被测介质,测量准确度几乎不受介质温度、压力等参数的影响等优点,尤其是在大管径流量测量方面,其优越性更为明显。 The ultrasonic flowmeter has the advantages of not contacting the measured medium, and the measurement accuracy is hardly affected by parameters such as temperature and pressure of the medium. Especially in the measurement of large diameter flow, its advantages are more obvious. According to the actual production, Dalian Sony Card Instrument Co., Ltd.'s FV2000F ultrasonic flowmeter was installed on the DN1000 cast iron pipeline of industrial circulating water with an accuracy of 1%. In order to prevent the fixture from being deformed due to the temperature and the contamination of the pipe wall surface, the ultrasonic wave cannot be received normally. A special guide clamp is used to keep the relative position of the two probes of the ultrasonic wave unchanged, which ensures accurate measurement. Due to the continuity of equipment production in petroleum refining and chemical enterprises, the most economical and convenient method for non-stop water measurement should be the ultrasonic flowmeter.

,一种为多普勒超声波流量计,另一类为时差式超声波流量计。 At present, two types of ultrasonic flowmeters are generally used, one is a Doppler ultrasonic flowmeter and the other is a time difference ultrasonic flowmeter. The Doppler type uses the phase difference method to measure the flow velocity, that is, a sound wave of a known frequency moves in the fluid. Because the liquid itself has a speed of movement, the frequency or phase of the ultrasonic wave changes between the two receivers or transmitters. By measuring this relative change, the velocity of the liquid can be obtained; the time difference type uses the time difference method to measure the flow velocity, that is, the sound wave of a certain speed changes its propagation time between the two receivers due to the fluid flow. By measuring this relative The change can obtain the fluid flow rate. Ultrasonic flowmeter operation and inspection work: (1) Instrument panel keyboard operation: Before starting the instrument operation, the parameters must be effectively set, for example, using the unit system, installation method, pipe diameter, pipe wall thickness, pipe material, and rough pipe Degree, fluid type, distance between two probes, flow rate unit, minimum speed, maximum speed, etc. Only when all parameters are entered correctly, the meter can correctly display the actual flow value. (2) Zero flow inspection, when the pipeline liquid is still, and there is no strong magnetic field interference or strong vibration around the meter, the meter display is zero. At this time, the zero point is automatically set to eliminate the zero point drift. Small signals must be cut off during operation. , Usually the flow rate is less than 5% of the full range flow rate, automatic removal. The zero point can also be adjusted through the menu. (3) Periodic calibration of the flowmeter. In order to ensure the accuracy of the flowmeter, we perform periodic calibration. Usually, we use a more accurate portable flowmeter for direct comparison, and use the measured data to calculate: error = (measurement Value-standard value) / standard value, using the calculated relative error and correction coefficient, so that the measurement error meets the error of ± 2%, and the measurement requirements can be met. The operation is simple and convenient, which can effectively improve the accuracy of measurement.