一、直流电流档
1、50μA 的电流档由46.2μA 表头、电位器WH1、电位器WH
2、R21组成。 V
A
V
25.01345.0115.050=+=μ
V
V V V V
V A
I V V V V V V V
V K 1.9918994102.11010)45002250180036084(102.1102.4954494102.11010)2250180036084(102.1102.2472244102.11010)180036084(102.1102.1102.60504150
250000505075.4925.010)8001503015(105025.01075.925.010)1503015(105025.05.225.225.010)3015(105025.0175.025.010********.03361336500336250
25036503610365.2361=??=?++++??==??=?+++??==??=?++??==+=+==+=?+++??+==+=?++??+==+=?+??+==+=???+=----------μ
V
V V V V
V A I K 76.100089941027.11110)45002250180036084(1027.11104.50044941027.11110)2250180036084(1027.11168.24922441027.11110)180036084(1027.11127.11127.61504080
250000
503361336500336250
250=??=?++++??==??=?+++??==??=?++??==+=+=------μ
二、电阻档(欧姆档)
万用表的欧姆档,其原理实质是用伏安法测电阻。它是将测量时用的电压固定,以电流值的大小去反映被测电阻值的大小, 图三是MF-47型直流电阻档工作原理电路图