Test for determining polarity of electrolytic capacitors within electronic assemblies

Abstract

A method of determining whether an electrolytic capacitor is properly connected or reversed in an electronic assembly. In a first embodiment, a non-contacting probe is placed near but not touching the body of the device under test (DUT). One terminal of the DUT is driven by a stimulus (voltage source or current source) while the other terminal is connected to a reference voltage. A voltage is measured at the probe relative to the reference voltage and the device is properly oriented if the measured voltage exceeds a predetermined threshold. In a second embodiment, current through the probe is measured instead of voltage at the probe. In a third embodiment, a non-contacting probe is placed near but not touching both leads of the DUT. Each DUT lead is alternately driven by a stimulus and alternately connected to a reference voltage. For each of the two lead test configurations, a voltage at each DUT lead is measured and current through the non-contacting probe is measured. Two algebraic electromagnetic coupling coefficients are computed from the four voltage measurements and the two current measurements. The relative size of the electromagnetic coupling coefficients determines the measured polarity of the DUT. An alternative configuration for any of the embodiments is to drive the probe instead of a terminal of the DUT.