A double-Gerdien instrument for simultaneous bipolar air conductivity measurements on balloon platforms
Nicoll, K. A. and Harrison, R.G. (2008) A double-Gerdien instrument for simultaneous bipolar air conductivity measurements on balloon platforms. Review of Scientific Instruments, 79 (8). 084502 . ISSN 0034-6748
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To link to this article DOI: 10.1063/1.2964927
A bipolar air conductivity instrument is described for use with a standard disposable meteorological radiosonde package. It is intended to provide electrical measurements at cloud boundaries, where the ratio of the bipolar air conductivities is affected by the presence of charged particles. The sensors are two identical Gerdien-type electrodes, which, through a voltage decay method, measure positive and negative air conductivities simultaneously. Voltage decay provides a thermally stable approach and a novel low current leakage electrometer switch is described which initiates the decay sequence. The radiosonde supplies power and telemetry, as well as measuring simultaneous meteorological data. A test flight using a tethered balloon determined positive (σ+) and negative (σ−) conductivities of σ+ = 2.77±0.2 fS m−1 and σ− = 2.82±0.2 fS m−1, respectively, at 400 m aloft, with σ+/σ− = 0.98±0.04.