外文翻譯---基于聲學(xué)駐波的液位檢測方法

1、附錄 附錄 2 中英文翻譯 中英文翻譯英文原文： 英文原文：A New Level Measurement Method based on Acoustic Standing WaveWang Zhi Wen Cheng-lin Xu Xiao-bin Li Zhi-liangHangzhou DianzhiUniversityEmail:metero3377692@126.comAbstractA new lev

2、el measurement method based on acoustic standing wave is presented. Firstly, the system model about the frequencies of the acoustic standing waves is established and Kalman Filter is used to preprocess the standing wave

3、 frequency. It will increase the accuracy of level measurement by reducing the influence of environment noise and measurement error, which are usually ignored by most of acoustic level measurement methods. Secondly, the

4、 new conversion technique can be given to calculate the level height with estimates of standing wave frequencies from Kalman Filter. And it can overcome the strict limitation about frequency range in existing classical m

5、ethod. Moreover, the experiments show the proposed method effective.1. IntroductionThe level measurement methods based on sound reflection phenomena have been used successfully in some areas of the process industry [1-2

6、] (waste water treatment, chemical, petroleum, etc.). And the method based on the acoustic standing wave reflection is important among them. The sound waves are emitted vertical to the liquid surface and the echo signal

7、s will be sent to the controller. Then the level height will be calculated by terms of the character of the standing waves extracted from the echo signals [3].The common standing wave methods are simply equipped with sin

8、gle waveguide tube. It is necessary to measure sound velocity for accurate calculation of level height. However, the exact value of sound velocity can hardly computed, because it’s a complex physical quantity related mai

9、nly to temperature, gas amplitude and the velocity, standing waves will be formed [7]. When the sound waves travel in the direction vertical to the level, the above conditions can be satisfied. Let y1 be the acoustic wa

10、ve from the transmitter and y2 be the reflection of y1 through the liquid surface. Expressionsof both are respectivelyy 1 = A cos 2 π ( ft ? L λ ) (1)y 2 = A cos 2 π ( ft + L λ ) (2)And their synthesized wave isy = 2 A c

11、os(2 π L λ )cos(2 π ft)(3)Where A is the amplitude of acoustic wave, f is the frequency, L is the distance from the liquid surface to the top of tube, λ is the wavelength of the acoustic wave. L is the level height neede

12、d to be calculated. When λ and L satisfy the relation belowL = 2 n λ , n = 1,2,... (4)the amplitude of the synthesized wave will reach the peak. Its wavelength is λ=c/f , and thenL = nc (2f ) (5)Where c is the sound