A Simple Wireless Intra-Oral Thermometry

—A Denture with a CMOS Chip—

Abstract

A wireless intra-oral device has been fabricated to measure the temperature in a mouth. It contains a silicon CMOS chip attached printed circuit board and a button battery. A ring oscillator on the chip generates continuous wave which frequency depends on ambient temperature. The frequency shift is detected by a short wave radio wirelessly at the distance of 30 cm. The circuit draws 51 μA from a 1.55 V silver-oxide button battery for watches and it gives more than ten days running time.