Field resistance is temperature corrected and compared to nameplate information for condition assessment.  Accurate temperature of the field winding is required for proper comparison to the nameplate field resistance calculations.  Incorrect nameplate information may also create an invalid reference for resistance and a potential alarm condition.  If the corrected field resistance is significantly different than the value of resistance calculated from the nameplate voltage and current, verify the nameplate information is valid, refer to the operating manual for information on the expected field resistance, ensure the dissipation resistors are disconnected, and test directly on the slip rings, in an effort to isolate the cause. Remember, the difference may actually be a field anomaly and not a problem with the nameplate or temperature entry.