Abstract: A probe unit for automatic determination of quality properties in meat comprises an insertion probe with a measuring device, such as a light reflection meter, at a free end of the probe. A double-acting drive cylinder unit reciprocatingly moves the insertion probe and consists of an interior pipe surrounded by an outer impact resistant pipe. A tubular piston rod is reciprocatingly slidably arranged in the interior pipe. The piston rod extends through both ends of the interior pipe and has an overall length at least twice the length of its stroke. The front end of the piston rod serves as the insertion probe while the rear end of the piston rod carries or forms part of a position meter producing electric pulses indicative of the position of the light reflection meter with respect to the interior pipe. The position meter includes a signal generator with a toothed wheel engaging a toothed rack and generates pulses applied to a pulse counter.