a clinical thermometer for detecting an infrared ray radiated from a tympanic membrane eliminates thermometric errors caused by differences from one patient to another and variations in thermometric operations , to always perform stable , accurate thermometry . a clinical thermometer converts infrared radiation from a substantially tympanic membrane into an electrical signal to perform temperature detection , the thermometer including an almost cylindrical probe body . a constricted diameter portion formed at one end of the probe body can be inserted into an external auditory meatus and deformed so as to conform to a shape of the external auditory meatus . an infrared sensor incorporated in the constricted diameter portion is thereby arranged to receive radiation from the tympanic membrane .