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On-site manual liquid level measurement is the most common river water level monitoring method before the appearance of ultrasonic water level meter. However, with the development of technology, the shortcomings of this simple and primitive method are becoming more and more obvious. The error of manual liquid level measurement is relatively large, and it is easily affected by bad weather. More manpower is needed to monitor various field data every day, and it is risky to measure along a river with a depth of 5 meters.
However, with the introduction of ultrasonic level meter, liquid level measurement becomes simple and accurate to use. It is suitable for various complex working conditions and outdoor environment, which gradually replaces manual inspection method and becomes the main method of river water level monitoring. What are the ultrasonic liquid level measurement methods? How do we apply it to water level monitoring?
Ultrasonic sensors for detecting water level monitor water level by calculating the time required for transmission and reception or changing distance. It is convenient and stable to use, and is widely used in the field of liquid level measurement. At present, the common methods of ultrasonic liquid level measurement include resonance method, frequency difference method, ultrasonic attenuation method, ultrasonic pulse echo method and so on.
The principle of resonance method is to set a standing wave resonance state between the probe and the liquid surface according to the frequency of ultrasonic waves. The distance between the probe and the liquid level is proportional to the ultrasonic wavelength of the medium. Therefore, if the ultrasonic velocity is known, the wavelength at the resonance frequency can be calculated and the distance from the probe to the liquid surface can be converted.
Ultrasonic pulse echo method uses the principle of ultrasonic probe transmitting ultrasonic pulse to measure liquid level. Ultrasonic waves will reflect when they encounter obstacles d3220089-300x300. According to the ultrasonic waves in the current environment, the MCU records the ultrasonic transmission time and echo receiving time. The liquid surface height can be measured by the formula S=Ct/2 (S is the measurement distance, C is the ultrasonic propagation speed and t is the echo time).
Ultrasonic attenuation measurement is based on the principle that ultrasonic attenuation changes with distance in measuring medium. It measures the water level according to the attenuation change between the received signal and the transmitted signal.
The frequency difference method transmits frequency modulated ultrasonic waves through an ultrasonic probe. The frequency of ultrasonic wave changes with the propagation distance. According to the frequency difference between the received signal and the transmitted signal, the time from transmission to reception can be obtained.
From the above comparison of ultrasonic liquid level measurement methods, it can be seen that the frequency difference method requires the frequency modulator to generate modulation frequency. The attenuation method needs to measure the attenuation of ultrasonic waves. The detection level of resonance method is limited by specific conditions, and it needs to establish standing wave relationship with liquid surface, which belongs to contact measurement method. On the contrary, the ultrasonic pulse echo method does not need to set the liquid level and standing wave, and can carry out non-contact detection. Therefore, ultrasonic pulse echo water level monitoring is the most suitable method among several measurement methods.
Secondly, the application of ultrasonic water level meter in water level monitoring is as follows. Ultrasonic water level meter uses ultrasonic pulse echo method to measure water level. Especially, the transducer (probe) of the ultrasonic water level meter sends out high-frequency ultrasonic pulses, which are reflected when they meet the liquid surface. Part of the reflected echoes are received by the transducer (probe) and converted into electrical signals, so that users can know the water level almost in real time according to the reflected signals.
Besides using ultrasonic water level meter to monitor water level, users can also use radar, depth water level sensor and other technologies to monitor water level. Ultrasonic water level meter is a liquid level measuring instrument with low maintenance cost and wide application range. Users can get all the required data accurately, which is cost-effective and welcomed by many users.
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