Failure to take appropriate precautions can result in hazardous potentials which could be harmful to both personnel and test equipment. It should be noted that transformer windings are essentially large inductors. If the instrument will not energize the transformer at the highest current output, check connections and try again. Then, if necessary, reduce the current to the next lower value and repeat. Failure to discharge the winding could damage the instrument.
Measurements Wait until the display has stabilized prior to recording resistance values.
Generally, readings should stabilize in 10-15 seconds. However, the time required for readings to stabilize will vary based on the rating of the transformer, the winding configuration and the current output selected. On large transformers with high inductance windings it could take one to two minutes for readings to stabilize. If the readings don't stabilize within two minutes, check leads, connections and instrument. It may be necessary to reduce the test current.