Rinaldo J. Brun, Joseph Levine, Kenneth S. Kleinknecht
naca-tn-2458
Sep 1951
A flight instrument that uses electric means for measuring the droplet-size distribution in above-freezing clouds has been devised and given preliminary evaluation in flight. An electric charge is place on the droplets and they are separated aerodynamically according to their mass.
An Adobe Acrobat (PDF) file of the entire report:
http://naca.central.cranfield.ac.uk/reports/1951/naca-tn-2458.pdf