Matsushita Electric Industrial Co., Ltd.

Kimiaki Yamaguchi

Isao Kasai

Mitsuo Akiyoshi

Shinichi Sakai

Masaaki Sano

Susumu Murakami

Akinori Otsuka

A heating apparatus such as a microwave oven in which thermal energy of high-temperature vapor generated by heating an object is detected by a pyroelectric element and a resulting detection signal is used to control (stop) a heat source such as a microwave source, etc. Among AC voltages generated by the pyroelectric element due to heat exchange of the pyroelectric element, a voltage of a polarity generated at the time of heat discharge (temperature decrease) of the pyroelectric element is selected through a circuit means. A voltage generated by heat exchange between air moving slowly in a heating chamber and the pyroelectric element caused by the rotation of a turntable or the like is eliminated by another circuit means. A control section controls the operation of the heat source by deciding an output signal of the pyroelectric element by comparing it with a detection level determined in accordance with a noise level for a predetermined length of time after the start of the heating operation. Erroneous detection is thus prevented which otherwise might be caused by a noise voltage generated in the pyroelectric element by the thermal energy of a hot air staying in the heating chamber after the energization of the heat source or second heat source.

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Nara, Japan

Akinori Otsuka