Sunday, 3 May 2015

Issue Measuring Resistance Of Inductive Devices Wtih A Keysight U3401A

Recently i was measuring the resistance of a small transformer and saw an unusual problem with my Keysight U3401A Bench DMM.

By simply measuring the resistance of the windings on a small mains transformer when the measurement is taken and you remove the test lead from the transformer the DMM gets a small inductive kick from the transformer. This causes the DMM to display unusual numbers and work incorrectly.

The effect can be reset by changing measuring mode to volts and back to resistance or by power cycling the meter.

I would be interested to hear comments from those more experienced than i am about this. Could this be considered normal or is the DMM faulty of have poor design?

The effect is demonstrated in this video: