A.Theoretical Fundation
Ultrasonic Height Meter is developed based on the reflection priciple.. While sending a pulse signal, the built-in timer of reciever is activated, and stopped when reciever pick up reflected signal. By calculating the wave lenght and the time sensor spend on picking up reflected signal, the distance between the senor and the object,in this case is the ground, is measured.
Design Concept：
The Ultrasonic Height Meter consists of two modules: the distance sensing module, and the data displaying module.Among them, the data displaying module includes thress parts: timer, screen,and data processor.
The distance is measured by ultrasonic sensor. It translates the measured time interval betweent sending and recieving the signal into eletrical signal，which will be further picked up and transfered by A/D coverter. A screen will display the result.
B.System Structure
Ultrasonic Height Meter is a system control be microcontrollers ,and consist of ultrasound emission circuit and receiving circuit. The emission circuit is construted of circuit and the transducer located at the output port of emssion circuit. Ultrasond receiving circuit is consist of transducer,snubber circuit and a receiving intergrated circuit.
Ultrasonic sensor is a sensor that is developed accroding to the properties of ultrasound. Using ultrasound as a measuring tool, it must have both wave emission and receiving, and a sensor is needed to accomplish this job. Ultrasonic sensor is made of piezoeletraic ceramic, which can both emits and recieves ultrasound.
The core componet of ultrasonic sensor is the piezoelectric ceramic firm inside its metal or plastic case. The main parameters of its performance are working frequency, sensitivitym and working temperature.
C.Ultrasound Emitter
In order to reserch and use ultrasound, people have designed and produced a large variety of ultrasound emitters. They can be categorized into two types：electrical etimitting and mechanical emitting. The electrical way is the more commonly used.And the working principle of that can be found on wikipedia.
souce:http://www.chinabaike.com/t/9836/2013/0919/1579358.html
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