Dave tears down the Keithley 617 Electrometer, capable of measuring sub-femtoamp (attoamps!) resolution. Low Level Measurement Handbook: http://www.tek.com/sites/tek.com/files/media/document/resources/LowLevelHandbook_7Ed.pdf Forum: http://www.eevblog.com/forum/blog/eevblog-1017-enter-the-world-of-atto-amps/ Video on the relay matrix: https://www.youtube.com/watch?v=-mavHYV-H6o