Response of planar and cylindrical ion counters to a corona ion source

Because of the environmental and economic applications of small air ions near HVDC power lines, it is desirable to have accurate and reliable ion counters. A parallel-screen small air ion source using corona discharge was constructed for evaluating two aspiration ion counters in the range 5000 to 1,000,000 cm with positive and negative ions. A planar electrode ion counter and a cylindrical electrode ion counter were exposed to the ion source. Comparisons were made between predicted theoretical ion densities and those measured by two instruments. For a theoretical ion density of 10000 cm^-3 and a calibration-region spacing of 10 cm, both ion counters measured ion concentrations up to two times larger than the theoretical ion concentration in the calibration region. With the same theoretical ion density but with a calibration-region spacing of 30 cm, the planar ion counter measured within about 10% of the theoretical ion density