A two C range potential difference meter applying transposition branch is prepared as using 18x 10 omega as the first measuring disc, 10x 1.1 omega as the second measuring disc and 0 C 12.1 omega slide wire disc as the third measuring disc, using conducting wire to connect two measuring end buttons directly to three measuring discs to exclude contact resistance and variation as well as thermo voltage from measuring C stepping switch out of measuring result and to carry out compensation by large negative potential if zero potential is big; applying two resistances of 200 omega and 1800 omega to execute range changeover by utilizing transposition branch. |