说明：  介绍如何简单可靠而方便测量 4～20mA 信号的文章。许多仪器仪表在远距离传送信号时，都有可能采取 4～20mA 的方式进行传送。本文对使用运算放大器或者不用运算放大器的场合都有介绍。给出了接口电阻的计算方法以及调整4mA＝零点，20mA＝满度的详细说明。并附有局部连接的原理图。
(How simple, reliable and convenient measurement of 4 ~ 20mA signal article. Many instruments in the long-distance signal transmission, may take 4 ~ 20mA way transmission. In this paper, an operational amplifier or op amp do not have a description occasions. Shows the calculation of the interface resistance and adjust the 4mA = zero, 20mA = full scale details. Local connections together with the schematic.)