超声波测距外文文献加中文翻译-毕业设计

1、附录a英文原版ULTASONIC RANGING IN AIRg . e . rudashvski and a . a . gorbatovudc 534，321.93336931.71.083.7one of the most important problems in instrumentation technology is the remote，Contactless measurement of distances in the order of 0.2 to 10m inthe physical properties of air，in which the measurements

2、 are made，Permit vibrations to be employeed at frequencies up to 500 khz for distanciesthe problem of measureing distances in air is some hat different from other problems in the a-pplication of ultra stered .although the possibility of usin G acoustic ranging for this purpose has been known for a l

3、ong time，and at first glance appears very simple，NAT first glance appears very simplethe main diff Icu lty here is in providing a reliable acoustic three-dimensional contact with the test object during sever changes in the airs charactespractically all acoustic arrangemes presently known for checkin

4、g distances use a method of measureing the propagation time for certain informationthe unmodulated acoustic Vibrations radiated by a transdumer are not in themselves a source of information。in order to transmit some informational communication that can then b E selected at The receiving end after re

5、flection from The test member，The rrein this case the ultraonic vibrations are the carrier of the information which lies in the modulation signal，i.e .they are the means forThis conclusion，however，does not mean that the analysis and selection of parameters for the carrier vibrations is of minor impo

6、rtance。on the contrry，The frequency of The carrier vibrations is linked in a very close manner With The coding method for The informational communicationlet us dwell on the questions of general importance for ultra steronic ranging in air，namely 3360 on the choice of a carrier frequency and the amou

7、ncyan analysis shows that with conical dirt diagrams for The radiator And receiver，And assuming that The distance between radiator And receiver iswhere prad is the amount of acoustic power radiated，b is the absorption coefficient for a plane wave in the medium，L is the distance between theBoth in eq

8、。(1) and below，the absorption coefficient is dependent on the amplitude and not on the intensity as in someworks1，and thereforein The various problems of soundranging on The test members of machines and structures，The relationship between The signal attenuation s due toit must be pointed out that th

9、e choice Of the geometrical parameters for the beam in specific practical cases is dictated by the shape Of the refleting sshapelet us consider in more detail the relationship between the geometric and the power parameters of acoustic beams for the most common cases of ranging ofit is well known tha

10、t the directional character istic w of a circular piston vibrating in an infinite baffle is a function of the ratio of the pistons d Ia(2)where JL is a Bessel function of the first order and alpha is the angle between a normal to the piston and a line projected from the center of the piston to the p

11、opos来自eq。(2)it is readyly found that a t w o-t o-o n e reduction in the sensitivity of a radiator with respect to sound pressure will occur at the angle(3)for angles20 . eq .(3)can be simplified to(4)where c is the velocity of sound in the medi MAA and f is the frequency of the radiated vibrations。It follows from eq。(4)that when radiation into air where c=330m/s e c，The neceary diameter of The radiator fo