measure padas
industry design and validation may use two method to measure pad capacitance, one of them is simple LRC meter, which adopted a electrical bridge connection and tune all the legs to be balanced and calculate the cap (all of the tunning operation is automatic). the other way is using TDR unit, which is an expensive equipement, by sending out a very narrow pulse to a socket with/without unit plugged in, then mesure the returned signal waveform, by analying the differences of these two waveforms, the load cap can be calculated.