CONTINUOUSLY CALIBRATING TEMPERATURE CONTROLLER

摘要

A multiple-loop temperature controller using RTD sensors is continuously calibrated by performing a zero or full scale calibration during each operating cycle. An arrangement of four multiplexers is used to successively connect each RTD sensor to a pair of current sources and an A/D converter, thereby allowing the current sources and A/D converter to be shared among all of the RTD sensors. Measurement errors are minimized by using the same multiplexers for temperature measurement and calibration, with calibration being performed by connecting the multiplexers to a ground reference or precision resistor. Interrupt-driven temperature loop processing is used to reduce A/D conversion delays, thereby allowing high-precision A/D converters with long settling times to be used. The multiple-loop temperature controller is advantageously utilized in an automated blood culturing system requiring precise control of sample temperatures.