In order to detect incursions of air into the glass tubes of incandescent lamps and discharge lamps which are evacuated or filled with protective (inert) gas (e.g. N2, N2/Ar), a radio-frequency/high-voltage spark discharge is carried out by means of a tesla transformer between the probe tip (test prod) and glass tube. In the case of non-defective lamps, which have a low pressure of filling gas, a maximum spark gap occurs, while in the case of defective lamps there is a shortening of the maximum spark gap, depending on the additional atmospheric and partial pressure.
