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一、前言用低分辨率(8位)逐次逼近型A/D和D/A芯片组成高分辨率(14～16位)A/D转换电路能以较低的代价换取较高的转换速率和分辨率,在目前高分辨率逐次逼近型A/D器件尚相当昂贵的情况下是可取的。但如果该类电路的精度仍只能保持8位,即其低位数值(8～13位或15位)并非输入模拟器的正确反映,并且其差值亦不是一个恒量,则它的实用意义仍不大。对于测控系统而言,或许只是无谓地耗费了系统的资源(包括CPU,总线和RAM等),而没有达到提高精度的目的。本文拟以一个8位A/D和8位D/A芯片组成的15位A/D转换电路为例,对可能产生的误差作一简单的分析,并介绍软件补偿方法。
I. INTRODUCTION High-resolution (14 ~ 16-bit) A / D conversion circuits can be used in low resolution (8 bit) successive approximation type A / D and D / A chips to exchange higher conversion rates Resolution is desirable in the current high-resolution successive approximation type A / D devices that are still relatively expensive. However, if the accuracy of such circuits can only be kept at 8 bits, that is, the low value (8 ~ 13 bits or 15 bits) is not the correct reflection of the input simulator, and the difference is not a constant, then its practical significance Not big. For the measurement and control system, perhaps only unnecessary use of system resources (including CPU, bus and RAM, etc.), but did not achieve the purpose of improving accuracy. In this paper, a 15-bit A / D conversion circuit composed of 8-bit A / D and 8-bit D / A chips is taken as an example to make a simple analysis on the possible errors and to introduce the software compensation method.