VERFAHREN UND VORRICHTUNG ZUR OPTISCHEN MESSUNG DER KONZENTRATION EINES ANALYTEN

Apparatus and method in which a beam of radiant energy (16) is passed into a medium at a wavelength selected to cause a response of an analyte in the medium or of a sensor (10,14) exposed to the medium, the sensor comprising a reagent whose optical properties change in response to the presence of the analyte in the medium. A perturbing pulse of energy (22) is passed into the medium to alter the response of the analyte or reagent to the beam of radiation; and the time rates of change in the intensity of the transmitted radiant energy are measured (18,24,26,28) while the intensity is changing due to the perturbing pulse, after each such perturbing pulse starts or ends or both, such rates of change being proportional to the concentration of the analyte in the medium. Both the beam of radiant energy and the perturbing pulse may be passed through optic fibers into the medium or sensor.