The Research And Development Of An Automatic Quantitative Weighing Control Instrument

The demand for automatic quantitative weighing apparatus in our country is quite large, but the automatic quantitative weighing control instrument technology of our country is still relatively behind the times. So a quantitative weighing control instrument is developed in this dissertation, and it has the characteristics of high control accuracy, practical functions and stable and reliable performance etc.This instrument can be classified into embedded microcontroller system, and the microcontroller unit employed in this system is ATmega 32L.The hardware circuits designed include: signal conditioning circuit, data acquisition circuit, display and keyboard circuit, system input and output circuit, system power supply and monitoring circuit etc. To ensure the precision and accuracy of the system, the resistance strain meter type load cell that is of high sensitivity and stable performance andΔ?Σtype 24 bits high resolution analog-digital converting chip ADS1251 are selected. By programming the software of the system, several practical functions, such as the automatic control of three-stage feeding quantitative weighing process, automatic correction of closing lead data, automatic storage of package data, keyboard operation and real-time display etc, are accomplished by the instrument. In addition to hardware filtering measures, digital filtering technology accomplished by software is employed as well. By changing the filtering depth factor in the arithmetic model of digital filtering algorithm, the weighing accuracy of the system can be adjusted accordingly. Three soft ware control strategies are employed to resolve satisfactorily the contradiction between measuring rate and accuracy, and they are comparison and judgment prohibited method, automatic correction of closing lead and oversize deviation warning. Experimental tests on stability, static performance and dynamic performance of the system are conducted respectively. And the analysis of testing reports indicate that the stability and the accuracy and precision of automatic quantitative weighing control of this instrument are in accordance with the desired technical properties. While summarizing the research work, some suggestions and tentative plans on the futuristic innovation and improvement of this instrument are proposed.