Abstract: The present invention comprises a method for testing the accuracy and the reliability of a thermal unit of a thermal cycler or of an enclosure of a PCR thermal cycler thermally controlled by pulsed air, said thermal unit and enclosure thermally controlled by pulsed air comprising a plurality of locations for reaction mixture tubes, said method comprising the following steps: a) arranging a set of temperature-measuring sensors in locations for reaction mixture tubes selected in said thermal unit and enclosure thermally controlled by pulsed air, said temperature-measuring sensors comprising: (i) a reaction tube suited to the type of thermal unit tested, (ii) a selected volume of liquid at least partially filling said reaction tube, (iii) a thermal probe at least partially submerged in said liquid, and (iv) at least one means for linking said thermal probe to a means for receiving a signal generated by said thermal probe, ?said locations in which said temperature-measuring sensors are arranged being distri