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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).