Lifetime control: the vacuum chamber accomodating the filled envelopes is flushed with helium before sealing. The leaking rate of the insulating component is analysed by using a helium detector.
An important parameter for the prediction of the life time of a VIP.
Laser distance control: A least time consuming method to qualify VIP's as „good“ or „not good“ by monitoring the dilatation of the surface of a VIP while being exposed to a variation of external pressures. Selected values of foil – dilatation are programmed and shown to the operator by means of a green or red light.