A new tympanic thermometer is analyzed and tested experimentally. An electrically calibrated pyroelectric detector of special configuration is employed to determine a person’s body temperature. An energy-storage, power-supply-isolated capacitor is used as the electrical heating reference. The new thermometer design has an accuracy within 60.1 °C with a 90% confidence and is immune to ambient temperature, detector aging, and parameter variations. An equivalent-circuit model is established in the analysis to account for the heat exchanges among the tympanum, the surroundings, and the detector as well as for the electrothermal behavior of the detector. The model provides effective simulation of the thermometer with PSPICE. Critical parameters governing the accuracy and the limitation of the tympanic thermometer are also pointed out by the simulation.