Module for measurement of CO2 concentration in exhaled air

The objective of this work consists in working out of a detection module for capnography (carbon dioxide concentration measurement in anaesthesiology and intensive care). The principle of operation of the module consists of the NDIR method. The basic assumption for construction of this model was using of directly modulated thermal IR source in it. A few models of IR sources were worked out. Their heaters were made from thick platinum layers and foil. Limits of modulation frequency for IR sources were greater than 30 Hz. The detection module consists of an optical part, analogue electronics and microprocessor system with a suitable program. The time dependent concentration of CO2, end tidal concentration of CO2, mean concentration of N2O and breath frequency are output values of the detection module. Measurements are executed 30 times per second. The accuracy of CO2 concentration measurement equals to 5%.