Paper presents the digitally controlled high resolution DC current transformer enabling contactless measurements of DC current. To increase the sensitivity of current transformer, high permeability, amorphous alloy based ring-shaped core was used. Moreover, analyses of magnetic field distribution in the measuring gap were carried out. Magnetic field in this gap was measured by the hall sensor connected with the high resolution sigma-delta analog to digital converter. As a result, current up to 100 A may be measured with uncertainty of about 1A.