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ADPD 1080 Oxygen saturation measurement

Category: Software


I'm using the ADPD 1080 on a custom board to develop a sensor that performs a transmission measurement of oxygen saturation on whole blood in a tube. I'm using the Beer-lambert law to compute optical density OD=-log(I-Idark/I0-Idark) and compute the absorption coefficient by dividing by the pathlength (~1 cm). However, I'm running into the issue of the light being heavily attenuated such that cannot make an accurate measurement (i.e. near the noise floor). I attempted to rectify this by increasing the gain from 25k\ohm to 100k\ohm and scaling my reference I0 by that factor keeping Idark (background measurement) the same. This didn't resolve the issue. I decided to see if there was something wrong with my settings and moved toward making measurements on an ink solution with known absorption coefficients. I found that at a constant gain of 25 I get values quiet close to the known parameter while at a constant 100 gain the measured values underestimate the actual coefficients. I'm thinking this implies something is wrong with either my alignment of the lasers and the integrator window or with the amplification itself. Any guidance/help would be much appreciated.

Thank you,

Osama Elgabori