Ultrasonic distance meter
Document Type and Number:United States Patent 5442592
Abstract:An ultrasonic distance meter cancels out the effects of temperature and humidity variations by including a measuring unit and a reference unit. In each of the units, a repetitive ries of puls is generated, each having a repetition rate directly related to the respective distance between an electroacoustic transmitter and an electroacoustic receiver. The pul trains are provided to respective counters, and the ratio of the counter outputs is utilized to determine the distance being measured.
versatility>花菜英文Publication Date:08/15/1995
Primary Examiner:Lobo, Ian J.
1、现代大学英语精读3BACKGROUND OF THE INVENTION
This invention relates to apparatus for the measurement of distance and, more particularly, to such apparatus which transmits ultrasonic waves between two points.
Precision machine tools must be calibrated. In the past, this has been accomplished utilizing mechanical devices such as calipers, micrometers, and the like. However, the u of such devices does not readily lend itlf to automation techniques. It is known that the distance between two points can be determined by measuring the propagation time of a wave travelling between tho two points. One such type of wave is an ultrasonic, or acoustic, wave. When an ultrasonic wave travels between two points, the distance between the two points can be measured by multiplying the transit time of the wave by the wave velocity in the medium parating the two points. It is therefore an object of the prent invention to provide apparatus utilizing ultrasonic waves to accurately measure the distance between two points.
When the medium between the two points who spacing is being measured is air, the sound velocity is dependent upon the temperature and humidity of the air. It is therefore a further object of the,prent invention to provide apparatus of the type described which is independent of temperature and humidity variations.
2、SUMMARY OF THE INVENTION
The foregoing and additional objects are attained in accordance with the principles of this invention by providing distance measuring apparatus which includes a reference unit and a measuring unit. The reference and measuring units are the same and each includes an electroacoustic transmitter and an electroacoustic receiver. The spacing between the transmitter and the receiver of the reference unit is a fixed reference distance, whereas the spacing between the transmitter and receiver of the measuring unit is the distance to be measured. In each of the units, the transmitter and receiver are coupled by a feedback loop which caus the transmitter to generate an acoustic pul which is received by the receiver and converted into an electrical pul which is then fed back to the transmitter, so that a repetitive ries of puls results. The repetition rate of the puls is inverly related to the distance between the transmitter and the receiver. In each of the units, the puls are provided to a counter. Since the reference distance is known, the ratio of the counter outputs is utilized to determine the desired distance to be measured. Since both counts are identically influenced by temperature and humidity variations, by taking the ratio of the counts, the resultant measurement becomes innsitive to such variations. 黄静怡
stateoftheart
生命在于运动英语3、BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing will be more readily apparent upon reading the following description in conjunction with the drawing in which the single FIGURE schematically depicts apparatus constructed in accordance with the principles of this invention.
背靠背的英文
4、DETAILED DESCRIPTION
Referring now to the drawing, there is shown a measuring unit 10 and a reference unit 12, both coupled to a utilization means 14. The measuring unit 10 includes an electroacoustic transmitter 16 and an electroacoustic receiver 18. The transmitter 16 includes piezoelectric material 20 sandwiched between a pair of electrodes 22 and 24. Likewi, the receiver 18 includes piezoelectric material 26 sandwiched between a pair of electrodes 28 and 30. As is known, by applying an electric field across the electrodes 22 and 24, stress is induced in the piezoelectric material 20. If the field varies, such as by the application of an electrical pul, an acoustic wave 32 is generated. As is further known, when an acoustic wave impinges upon the receiver 18, this induces stress in the
conferences
piezoelectric material 26 which caus an electrical signal to be generated across the electrodes 28 and 30. Although piezoelectric transducers have been illustrated, other electroacoustic devices may be utilized, such as, for example, electrostatic, electret or electromagnetic types.
英语必修五课文翻译everyone是什么意思
As shown, the electrodes 28 and 30 of the receiver 18 are coupled to the input of an amplifier 34, who output is coupled to the input of a detector 36. The detector 36 is arranged to provide a signal to the pul former 38 when the output from the amplifier 34 exceeds a predetermined level. The pul former 38 then generates a trigger pul which is provided to the pul generator 40. In order to enhance the nsitivity of the system, the transducers 16 and 18 are resonantly excited. There is accordingly provided a continuous wave oscillator 42 which provides a continuous oscillating signal at a fixed frequency, preferably the resonant frequency of the transducers 16 and 18. This oscillating signal is provided to the modulator 44. To effectively excite the transmitter 16, it is preferable to provide veral cycles of the resonant frequency signal, rather than a single pul or single cycle. Accordingly, the pul generator 40 is arranged, in respon
to the application thereto of a trigger pul, to provide a control pul to the modulator 44 having a time duration equal the time duration of a predetermined number of cycles of the oscillating signal from the oscillator 42. This control pul caus the modulator 44 to pass a "burst" of cycles to excite the transmitter 16.
