A control device for a contactor, in particular for scrolling through a menu which allows appliances in a motor vehicle to be controlled. Use of an alternative invasive or noninvasive glucose determination in the calibration allows minimization of errors due to sampling methodology, and spatial and temporal variation that are built into the calibration model. The brake fluid positively displaces any brake fluid containing gas from the vehicle brake system into the brake fluid reservoir, where gas bubbles can escape from the brake fluid.