Vibrating reed electrometer with sub-aA current resolution

An extremely sensitive vibrating reed electrometer is built, that is able to reach sub-aA current resolution within a one-minute measurement. The input leakage current of the set-up is -0.12 aA, that is less than 1 electron per second. Crucial for this extreme sensitivity and low leakage current is the development of an input stage with only vacuum gap capacitors. The stability and sensitivity of this new electrometer make it suitable for accurate low-frequency characterization of vacuum gap capacitors used in the electron counting capacitance standard experiment.