A grain measurement device (76) comprises a chamber (80) having an inlet (82) and an outlet (84) for grain that is to be tested. A spectrometer is equipped with a light source (89) and a detector (91) for light which was generated by the light source (89) and was transmitted through the sample. The detector (91) is connected to an analyzer (134) for wavelength-resolved analysis of the received light. A mounting (93) of one of the light source (89) or detector (91) can be moved with respect to the other (91, 89 by a drive (106), which moves the mounting (93) for purposes of conveying the sample either in the flow direction (130) or in the opposite direction, in order to break up the sample or to avoid bridging and/or jamming of the sample in the measurement chamber (80).