A digital thermometer with fast response and high precision

Body temperature is one of vital signs which can reflect physical status of an individual. Digital thermometers are adopted in clinical gradually in recent years. But few thermometers are really used in clinical because the measurement accuracy or measuring time. In the paper, we designed an improved digital thermometer which has both fast response and high precision. For excellent performance, 1) thermocouple and resistance temperature detector (RTD) are used to measure body temperature; 2) AD7793, high resolution and low noise analog-to-digital converter (ADC), digitalizes the results; 3) specific assemble and heat isolation methods are considered for better performance; 4) final calibration is realized to further improve the precision of thermometer. In addition, for making better use of reference tables of both thermocouple and RTD, least square method is used to realize second-order fitting without affecting precision of thermometer. The thermometer also contains other functions including display function, storage function, and wireless transmission function. Finally the digital thermometer is tested in the lab. And the improved thermometer can realize measurement within short time of 5 seconds and with high precision of 0.05 degree Celsius. Thus our thermometer makes it possible that digital thermometer can totally replace mercury thermometer in the future. With fast response and high precision, the digital thermometer can serve sufficiently in clinical.