A substrate system of the kind having a buffer region interposed between a silicon substrate proper and a nitride semiconductor region in order to make up for a difference in linear expansion coefficient therebetween. In one embodiment, power consumed by an integrated circuit under test is measured. Other features, aspects and objects of the invention can be obtained from a review of the specification, the figures and the claims. The method can be implemented manually, but preferably is automated by implementation on a computer through appropriate software. The control has an activation or a deactivation step of said delivery pump, by closing or opening said first clutch at a vehicle speed lower than a threshold higher than zero, and in a condition of decelerating vehicle, with the simultaneous opening or closing of said second clutch, and if said conditions are verified within an interval of time from an activation or deactivation request. wavelength content, for reliably directing electromagnetic radiation emitted by a source thereof in a common direction, for achromatically reducing spot size on a sample, and for directing different wavelengths into different detectors, in ellipsometer, polarizer or the like systems.