一个内阻Rg为2500欧姆,电流Ig为100μA的表头,如图,现要求将表头电压量程扩大为2.5V、50V、250V

电压量程扩大为2.5V、50V、250V,表头Ig为100μA满课度,根据欧姆定律 I = U/R ,
需要串联回路的总电阻分别为
Rz1 = U1/Ig = 2.5 / 100 = 0.025MΩ = 25KΩ
Rz2 = U2/Ig = 50 / 100 = 0.5MΩ=500KΩ
Rz3 = U3/Ig = 250 / 100 = 2.5MΩ = 2500KΩ
所需串联的电阻R1、R2、R3的阻值分别为
R1 = Rz1 - Rg = 25 - 2500/1000 = 22.5KΩ
R2 = Rz2 - Rg = 500 - 2500/1000 = 497.5KΩ
R3 = Rz3 - Rg = 2500 - 2500/1000 = 2497.5KΩ