射频控制器1805B直流替代原理及校准

DC substitution principle and calibration of 1805B RF control unit

四线法是精确测量小电阻时最常用的一种方法。射频控制器1805B作为微波功率计自动校准装置中(系统ⅡA)的重要组成部分,它的直流替代电路是由三个臂的惠斯通电桥组成,其每四个臂可以用两个100Ω的标准电阻等效代替。通过对标准电阻两端直流电压的准确测量,就可判断1805B在各档的直流替代功率是否满足要求,本文最后给出了直流替代功率所对应的直流电压范围。

The four wires method is in common use to accurately measure a little resistance.The model 1805B RF control unit is important part as automatic power meter calibration system （system Ⅱ A） ,whose DC substitution circuit is comprised of three legs of a resistive wheatstone bilge, whose forth leg is replaced with two 100Ω standard resistanee. By the accurate measuring to the voltage across the standard resistor, it can be known whether the DC substitution power of each range of the 1805B RF ccontrol unit meets our demands.Finally,the range of DC voltage corresponding to DC substitution power is provided.