a method and an apparatus for verifying or testing test substrates , i . e . wafers and other electronic semiconductor components , in a prober under defined thermal conditions . such a verifying apparatus , known to the person skilled in the art as a prober , has a housing having at least two housing sections , in one housing section of which , designated hereinafter as test chamber , the test substrate to be verified is held by a chuck and is set to a defined temperature , and in the other housing section of which , designated hereinafter as probe chamber , probes are held . for verification purposes , the test substrate and the probes are positioned relative to one another by means of at least one positioning device and the probes subsequently make contact with the test substrate .