A new technique for the measurement of corona field strength and current density in electrical precipitation

IN THE course of studies of the electrical precipitation of gas-borne dust, it became necessary to determine the electric-field strength in the negative space-charge region of a corona discharge in room air. However, no satisfactory technique for making such measurements was known to the writer or to the persons whom he consulted, nor did a brief survey of the literature offer anything of use. A number of attempts were made to use static probes of types encountered in electrostatics, but these were uniformly unsuccessful. Hence, it became necessary to develop an instrument based on a new principle. This principle makes use of the laws governing the charge picked up by a particle in a unipolar space-charge field as a function of field strength, current density, and time. Essentially, the quantities measured are the particle charge and the time spent by a particle in the field. By the use of the particle-charging laws, the values of the field strength E and of the current density i may be deduced.