When the DC current transformer under test has analog voltage output, the method of measuring error can be used. 

The method of measuring difference can reduce the influence of current source output fluctuation on error verification test. When the Conversion Coefficient of the standard and the tested transformer is the same, the standard resistance box is not needed. When the analog output of the transformer under test is greater than the standard output, the standard resistance box shall be moved to the output side of the transformer under test. Adjust the standard resistance box so that the actual ratio of the DC current comparator is equal to the rated ratio of the DC transformer being tested.