Conductivity Sensors
GERDIEN CONDUCTIVITY PROBE
This is a device designed to determine the electrical conductivity of the atmosphere. By using a capacitor exposed to a sample of air and measuring the time it takes for discharge, the electrical conductivity of the sample is determined. The Gerdien condenser probe has the ability to sense both positive and negative ion conductivities. The probe utilizes a concentric, cylindrical electrode geometry with the inner and outer electrodes serving as the collector/guard and return electrodes, respectively. The ion conductivity is determined by applying a voltage (V) that is swept linearly between the two electrodes over a 1-minute period, and measuring the resulting current (I). The slope of the I?V characteristic (dI/dV) provides the conductivity measurement. Special construction techniques were used at the collector input to reduce stray leakage currents and susceptibility to electromagnetic interference (EMI). The length of the collector is 6.4 cm. The inner electrode extends another 10 cm as a guard section that is used to mechanically support the center electrode and the inner electrode is recessed 3.8 cm from the leading edge of the outer cylinder. The whole assembly has a length of 20 cm and a mass of 0.286 kg. It was mounted via a 7.6 cm sidestrut to the underside of the aircraft. A separate electronics box contained the sweep and data amplifier electronics. This was used in the Altus Cumulus Electrification Study (ACES) on an uninhabited aerial vehicle (UAV).