APPARATUS FOR MEASURING CARBON DIOXIDE CONCENTRATION IN EXPIRED AIR Russian patent published in 2002 - IPC

FIELD: medicine. SUBSTANCE: apparatus has measuring chamber communicated with patient's respiratory tracts and equipped with supersonic emitter having audio signal reflector, temperature sensor and heater, which are connected to input and first output of thermostatic control unit, respectively, commutator, analog-to-digital converter, reference signal former, pulse generator whose first output is connected to supersonic emitter and to first input of amplifier, and second output to waiting multivibrator, amplifier whose second input is connected to output of waiting multivibrator, amplitude detector whose input is connected to output of amplifier, logarithmic converter whose output is connected to input of threshold device, and to first input of counter circuit whose second input is connected to output of threshold device, third input is connected to second output of thermostatic control unit, fourth and fifth inputs are adapted for controlling apparatus operational mode and for setting calibration point number. First output of counter circuit is connected to control input of logarithmic converter and to control input of threshold device and second output to input of indicator unit. One of commutator inputs is connected to amplitude detector output. Control input of commutator is connected to fourth output of counter circuit and output to first input of logarithmic converter. Third output of counter circuit is connected to input of analog-to-digital converter, whose output is connected to second input of logarithmic converter and to input of reference signal former. Reference signal former outputs are connected to respective input of commutator. EFFECT: increased efficiency and improved precision of measuring carbon dioxide concentration in expired air. 4 dwg