The Biddle 577500 / 57J Energized Winding Resistance Tester is used for measuring the dc resistance of ac energized windings, thus enabling the determination of winding temperature rise while the windings are operated under actual load conditions. The Biddle 57J is suitable for measuring the winding resistance of transformers, chokes, induction coils, heater coils, generators and all types of motors where there are no brushes in series with the circuit being measured. Measurements are possible on either single phase or three phase, three wire equipment.
The Biddle 577500 / 57J Tester is a modified Wheatstone bridge and is used as such on energized or deenergized samples. The Biddle Tester is completely self-contained and measurements are made by balancing the bridge by means of the measuring dials and the null detector. Resistance readings are taken directly from the Biddle 57J, no calculations or multipliers are necessary.