The Design Of Ultrasonic Level Measurement Device

The technique of fluid level detect is extremely widespread, for example: the measurement of meteorological water level , giant oil pot fluid level, and so on. Along with the advanced intelligent instrument conception, on the basis of development the electronic and the micro control chip, the fluid level instrument is taking on daily variations.At present, the function and the price fluid level are different between different factories and t different sizes, domestic products are relatively cheap, but the functions are simple, the precision is not high enough, the functions the Overseas imported products are relatively perfect , the precision is very high, but expensive. To some middle and small scale users, it is difficult to support its price, and also the service is not convenient. Therefore, it is necessary to develop one that is simple, convenient, precise, and cheap.Among so many fluid level appliances, the prospect of the application of ultrasonic measurement is cheerful. It is un -contact one and the price will be accepted by everyone, at the same time, erection sequence is convenient,. the precision is high enough.When we are familiar with ultrasonic measurement transmission characteristics,sensor structure, and the patterns of the operating, we choose to use T/R40-6 .when the design and the work are finished, we work out corresponding operating software, and put the newproducts through a preliminary test, the result is satisfied to the utmost degree.During the hardware design, we take the monolithic integrated circuit AT90S8535 monolithic integrated circuit smallest system as the core, make the use of the automatic detection and the data processing with the help of ultrasonic wave as the control signal to the fluid level, which manual intervention will be reduced in the survey process, providing to have the demonstration, the keyboard man-machine conversation contact surface, it makes the staff to the examination real-time monitoring convenient, through the miniature printer and PC machine, the preserved related data and the correspondence, could carry on the management well to the examination memory situation .Mainly including: Ultrasonic wave transmission circuit; Accepting circuit; Temperature compensation; and corresponding control circuit. The ultrasonic wave transmission circuit the 40KHZ pulse signal which sends the monolithic integrated circuit enlarges 20V, satisfies the ultrasonic sensor the actuation .The supersonic reception to the echo which accepts is carried on the electric circuit the enlargement and the reshaping, soon the echo signal transforms the monolithic integrated circuit the signal of will stop. The AT90S8535 monolithic integrated circuit is its core part, the primary mission is, sends out the pulse train to actuate the ultrasonic wave transmitting transducer and send out the ultrasonic wave, carries on the time through timer T1 to the ultrasonic wave transmission time, the temperature detecting, according to thetime and the related parameter which determines the calculation of distance, the volume and so on. The controlled variable input and the data demonstration, machine communication and data printout and so on.During the software designing, the utilization modularized program design concept, carries on to different functional procedure programs separately, this not only makes the entire software the level and the structure quite clear, but also advantages and software debugging and revision, software part altogether weight big module, the first is the ultrasonic wave actuation and the data processing module, the second is the function module. Function module is divided into the keyboard and the demonstration module, the printing model, display model, communication model and so on.Finally has carried on the analysis to this design measuring error, as well as proposed reduces erroneous the method, causes its survey to be more precise. In design, because needs to measure the distance is long (several meters to several meters), in view of supersonic wave amplitude when dissemination assumes the exponential decay the characteristic, maximum limit sharpens the driving force, carries on the multiple-step amplifications to the echo, has met the design requirements. We can use the temperature survey compensation method: Realizes the sonic speed indirect compensation using the temperature sensor actual temperature, carries on in the monolithic integrated circuit the data operates, joins the temperature the consideration. In order to increase the precision,has selected digital temperature sensor DS1722, DS1722 is an American MAXIM Corporation's section ,three serial port digital temperature sensor, its resolution may achieve 0.060C.May meet this design precision requirements. The experimental result indicated this design method may enhance the ultrasonic wave distance gauge the measuring accuracy and the hardware expenses is not big.The entire measuring appliance operation completes through the keyboard control, chooses the different pressed key to complete the different functions .The pulse echo law is the current ultrasonic wave liquid when we use many methods, through realizes the fluid position survey to the ultrasonic wave transit time survey. Therefore, the fluid position survey precision transformed as the time and the temperature measuring accuracy.This topic research is merely a start, when we want the function to be more stronger, the measuring accuracy higher ultrasonic wave fluid position instrumentation also needs to solve very many problems, like the precision problems, improvement problems, the market problems, and so on.Under the help of the teacher and my classmates, and in my endeavor, the topic has been finally completed, but because my ability and the time are limited, the overall system function should be perfected .The experimental work and an academic thesis must have some deficiency, awaiting for the criticism and pointing out mistakes.