一种数字式电子秤的研究与设计

Research and Design of A Digital Electronic Scales

随着科技的进步,电子秤原有的精度已经不能满足市场要求,影响其精度的因素主要有:传感器、模数转换器(ADC)的选择.文章提出一种简单实用并且精度高的电子秤设计方案,使测量精度得到大大提高.设计分四个模块:称重传感器、滤波电路、A/D转换电路,通过外部LED显示模块显示称量结果.电路应用电阻应变桥式传感器来采集电压的微小变化,通过电感与电容组成的抗干扰滤高频杂波作用的EMI滤波器,减小外部环境对电子秤电路的影响,由电阻和电容组成的一阶RC滤波器,用来限制输入信号的带宽,降低输入信号的噪声;经过内部集成差分放大电路和高性能的∑-ΔADC(过采样模数转换器)的A/D转换芯片AD7799,对输入电压信号进行放大并转换成数字量输出;显示模块采用驱动器PS7219驱动四位八段LED显示器构成,显示实际测量值.电子秤系统总体设计实现了测量精度的大幅度提高.另外,设计电路集成度高、抗噪声能力强、滤波效果显著,因而具有很好的系统稳定性和测量准确性.

Alongwith the progresses in technology, the accuracy of the original electronic scale can no longer meet the market requirements. Judging from the status, the factors affecting the accuracy are the selections of sensors and ADC. A simple practical and high - precision design of the electronic scale has been proposed in this research, which makes measurement accuracy be greatly enhance. The circuit is composed of four modules：weighing sensors, filtering, A/D conversion and external LED display module which display weighing results. Application of the resistance strain sensor in design to capture small changes in voltage;the EMI filter, composed of anti, clutter the role of high - frequency, to reduce the impact from external environment to the circuit, using the first - order RC filter, to limit the bandwidth of input signal, elbow input signal noise;using the A/D conversion chip AD7799 that contains the differential amplifier circuit and a high- performance ∑ -△ADC （over sampled ADC）, to enlarge the input voltage signal then convert it into digital output; using PS7219 to drive the LED displays which can show the actual measured values. The design of Electronic scale system achieve a substantial increase in measurement precision. In addition, its high integration density, strong noise resisting ability and obvious filtering effect for circuit, which make good stability and measurement accuracy for system.