A method is provided for measuring a state variable of a biological cell located in a nutrient medium and supported on and adhering to a support area. In one embodiment, the reels rotate horizontally and in different directions. The scoring mesh comprises interlacing filaments that extend from a mesh proximal end towards a mesh distal end, form distal filament loops at said mesh distal end, and then return to the mesh proximal end. By determining the location of such a dataflow interruption, the root cause of the control application fail can be determined. Insertion of the standard fitting can automatically open the cams, and springs can automatically return the cam levers to their locking positions.