V = k* V0
where k is a function of the air density d
d = p/760 * (293 / (273+T)) where p in Torr and T in degrees C
| d | 0.70 | 0.75 | 0.80 | 0.85 | 0.90 | 0.95 | 1.0 | 1.05 | 1.10 | 1.15 |
| k | 0.72 | 0.77 | 0.82 | 0.86 | 0.91 | 0.95 | 1.0 | 1.05 | 1.09 | 1.12 |
The voltage increases with humidity varying some 2-3% over a normal atmospheric range of 8-15 g/m3.
If the gap is illuminated with UV or X-rays, it is more easily ionized. The effect is more pronounced with smaller gaps, a 20% reduction for short gaps of a few cm when irradiated. For this reason, UV irradiation is specified for accurate breakdown voltage tests, particularly with smaller gaps.
Copyright 1998, Jim Lux / sgcorr.htm / 8 March 1998 / Back to HV Home / Back to home page / Mail to Jim