摘要:本次设计的对象是一个三位半直流数字电压表，量程为0~1.999V，误差为5 ‰V。该设计主要由3位A/D转换器、七路达林顿驱动器、七段译码/锁存/驱动器、基准电源和显示器组成。工作原理：A/D转换器将输入的模拟信号转换成数字信号；由基准电源提供精密电压，供A/D转换器作参考电压；在段驱动信号和位驱动信号共同作用下在显示器上显示所要测量的直流模拟电压。当被测电压超过基准电压时，过量程信号输出低电平，从而使显示数字熄灭，指示过量程状态。

　　　三位半数字电压表具有高精度、抗干扰能力强、低功耗、读书清晰直观等特点，是生产和实验中最常使用的测量仪器之一。

关键词：直流数字电压表；3位A/D转换器；驱动器；基准电源

Abstract:The design of the object is a three and a half DC digital voltage meter, range is 0 ~±1.999V, error is 5‰V. This design mainly consists of 3bit A/D converter, seven Darlington Driver, seven segment decoding / latch / driver, the reference power source and display. Working principle: A/D converter converting the input analog signal to digital signal; by the reference power supply voltage, for A/D converter as the reference voltage; the segment drive signals and a drive signal common role in the display shows the measured DC analog voltage. When the measured voltage exceeds the reference voltage, over range signal output low level, so that the display digital extinguished, indicative range state.

　　Three semi-digital voltage meter has the advantages of high precision, strong anti-jamming ability, low power consumption, reading is visual and clear features, is the production and experiment the most frequently used instrument.

Key words: DC digital voltage meter；3bit A / D converter；Driver；Reference power