Together with the piston sampler, the clinker sampler ranks amongst those samplers removing a selective sample from the material flow. For this purpose, a sampling spoon, which is filled with sample material over a defined period of time, is run into the product flow pneumatically. When the sampling spoon is drawn back, it is removed inside the sampler housing by a piston and the material sample pre-classified over a rigid sieve grid. The fine material thus obtained can be taken over for further analysis at a pipe socket. The coarse parts are taken over at a further pipe socket and fed to the principal material flow again.