A method for checking the soiling of the windows of a measuring apparatus for checking sheet material, includes having at least two sensor rows oriented transversally to the transport direction of the sheet material. A ribbon conductor is also wound with a plurality of selected number of turns along the aluminium tube. If a quality of service decreases, then the first device causes a second session to be set up where the second session uses the second air interface. the base color of the corolla throat is brilliant greenish yellow and the outside of the corolla tube is brilliant greenish yellow. A brake device is disposed in a radial direction of the sheave for braking a brake disc constructed so as to extend in the radial directions and secured to the sheave. The blade sharpening system also includes a sharpener slidably coupled to the rod and configured to engage a generally circular blade of an agricultural implement while the generally circular blade is mounted on the agricultural implement.