US Patent 11187746 Contact quality testing

An apparatus for automatic testing of an electronic device includes a pad interface unit and measurement circuitry. The pad interface unit is configured to connect to pads of the electronic device. The measurement circuitry is configured to select a circuit path in the electronic device that passes via a digital signal pad from among the pads, which is configured to carry a digital signal, to estimate a non-binary measure indicative of an electrical resistance of the circuit path, by performing current-voltage measurements using the pad interface unit, and to determine, based on the non-binary measure, whether the digital signal pad passes or fails a test.