Vibration Reed Electrometer for Accurate Measurement of Electrical Currents Below 10 pA

We have developed a home-built vibrating reed (VR) electrometer. The heart of the meter is a VR capacitor, which excels in a stable and low input leakage current of only 8 aA with a 2 aA noise for a 1 h measurement. This paper demonstrates that this makes the instrument ideal for the characterization of subtle charge effects in, for example, connectors and cables. The exceptional sensitivity of the electrometer is proven in a measurement of the leakage resistance of an air gap capacitor which results in a value of $R_{\rm leak} = (8.8 \pm 0.3)\cdot 10^{17}\ \Omega$, obtained at a test voltage of only 10 V. Calibration of the system with both a picoampere and a picocoulomb generator shows that the instrument has an accuracy of 15 parts in $10^{6}\, (k = 1)$ at a current of 1 pA. As far as we are aware, this is the best uncertainty for a room temperature electrometer published so far.