Design of an ultrasonic system for temperature measurement in an infant incubator

In this paper, we develop a binary frequency shift-keyed (BFSK) ultrasonic measurement method based on the speed of sound to measure the temperature. The proposed algorithm combines both time-of-flight (TOF) method and the phase-shift method. A single-chip microcomputer-based BFSK signal generator and phase detector was designed to record and compute the TOF, two phase shifts and the resulting temperature, which were then sent to PC. The PC is used for calibrating the system and recording or controlling the temperature in an infant incubator. Theoretically, the resolution of temperature was found to be within ±0.2°C when the distance between the transmitter and receiver is 1 m. But the temperature can be verified by with an accuracy of ±1°C by our laboratory prototype. The main advantage of this ultrasonic velocity measurement system is a quick and precise monitoring of the temperature in an infant incubator.