Abstract: An apparatus for cyclical temperature processes with automatic monitoring and adjusting of the temperature of a water bath, including a reactor space with a water bath in which a plurality of sample containers with samples to be examined can be placed. The desired temperatures and periods during which each adjusted temperature should be maintained are adjustable by an adjustment means, wherein a temperature sensor for measuring the temperature of the water bath is provided and a control unit controls the temperature of the water bath in dependence on the measured temperature and time. At least one magnetron tube is provided in the reactor space for heating the water bath and the sample containers placed in the same. The water bath is connectable to a water conduit through a water supply conduit wherein the control unit controls the magnetron tube and the valve in dependence on the desired temperature and time.