LOW COST MEANS FOR INCREASING MEASUREMENT SENSITIVITY IN LED/IRED NEAR-INFRARED INSTRUMENTS

摘要

A low cost means for increasing measurement sensitivity in LED/IRED near-infrared instruments is disclosed which utilizes a current modification means (27) for modifying the driving current supplied to each IRED (5) as a function of the opacity of the particular sample being measured. The current modification means is part of the processing means and comprises means for measuring a signal level (8) for each IRED at an analog-to-digital converter (10). Based upon the signal level detected for each IRED, the current modification means modifies the current to each IRED to a value that is as high as possible without saturating the analog-to-digital converter. Thus, by modifying the driving current of each IRED to such a maximal value, the analytical instrument of the present invention provides high resolution without the use of expensive electronic circuitry. Also provided is a system for generating and storing an optical signature of a particular user, thus further insuring the accuracy of measurements taken by the instrument.