Sources of error in transformer tests

Only those errors that have an appreciable effect upon the results need be considered. Instruments should be selected to give a reasonable scale deflection, should be calibrated at regular intervals, and should be used with discretion. The use of instrument transformers should be avoided wherever possible. Stray fields seriously affect readings. The ordinary tests that are made on transformers are enumerated and each one is considered separately. Sources of error in making these tests are pointed out and methods of avoiding or eliminating them are discussed.