pulse oximetry measures the relative concentration of arterial oxygenated hemoglobin and reduced hemoglobin. this paper presents the design of a pulse oximeter, which measures the presence of a third substance, carboxyhemoglobin (hbco), by unfiltered leds at 660 nm, 810 nm, and 940 nm. background information is given on the theory of pulse oximetry. theoretical approximations and calculations w...