Research And Design Of High-precision Electronic Balance

In this paper, by using of resistance strain sensor and high-precision ADC ADS1230, the weight signal will be turned into Digital signal, then send the digital signal to the processing microcontroller ATmega128L, and then displayed through the LCD. A buzzer circuit was designed, when the weight of objects weighing more than the maximum range, the buzzer will alarm. The system also set a key circuit, through the key to achieve better man-machine exchange. To reduce the temperature on the performance of electronic balance, the DS18B20 digital temperature sensor produced by the company of America DALLAS was used to sample the surrounding environment temperature of electronic balance, then can establish the temperature calibration curve. Finally, the electronic balance was calibrated by the least squares method.Firstly, the paper analyzes the development of electronic balance at home and abroad and the future direction of development. Secondly, the paper illustrates the working principle of the load cell and the methods of software and hardware compensation. Then the paper gives the overall framework of the system design. In this paper, the hardware design and software design aspects are introduced. The hardware design included power circuit design, the processor circuit design, Analog-digital conversion circuit design, LCD circuit design, JTAG circuit design. Focuses on the power circuit design and analog-digital conversion circuit design, because they are the key part of the whole system. the power circuit is stability or not related to the size of the final measurement error. The analog-digital conversion circuit is the core of the whole system, the design decisions have a direct result of the size of the error, in this paper, to reduce the influence caused by ADS1230 as much as possible, the analog and digital ground of ADS1230 were separated, the analog and digital power supply were separated too. This paper presents the design of each part of the circuit diagram, and describes the working principle of each part circuit. Software development tools used AVRStudio and IAR Embeddded Workbench. As a result of the C programming language, it can not be developed directly by AVRStudio, so need the help of third-party software IAR Embeddded Workbench. This paper describes the methods of the ADS1230 ADC program design, DS18B20 program design, key modules program design, liquid crystal display module program design. The paper draws a process flow chart and gives some important code, after each module code is completed, the main program calls each module code to achieve its function; then introduced the principle of the least square method and its application, the electronic balance was calibrated by the least square method; finally, performance of the whole system was tested and the sources of error was analyzed. This electronic balance scale was designed for the 0 - 100g, it can achieve the minimum scale is 0.01g, can be realized tare, clear, and overweight tips and other functions.