Current Aspects of Metrological Support to Optical Pulse Oximetry

It is shown that the metrological support system used throughout the world for optical pulse oximetry does not provide unification and an acceptable error level in measurements of blood oxygen saturation. A new method is proposed for calculating saturation and saturation errors, which enables one to reduce the measurement error to a level that meets current metrological specifications. Ways are considered of reducing the errors in optical pulse oximetry further.     

Influence of ionizing radiation on the parameters of an operational amplifier based on complementary bipolar transistors

The influence of a 4 MeV energy electron flux and 60Co gamma radiation with an average energy of 1.25 MeV on the characteristics of silicon complementary bipolar transistors (BTs) and a wide-band operational amplifier (OA) has been studied. It is established that an action of F_E = 3×10¹⁴ el/cm² electron fluence causes a decay in the common–emitter current gain (ß) of 61% for NPN and 66% for PNP transistors, as well as a decrease in the maximum value of the transition frequency (f_T) of 12% for NPN and by 4% for PNP transistors. When the absorbed dose D_G amounts to 3 Mrad, a decrease in ß by 39% for NPN and by 44% for PNP transistors, and in f_T of 10% for NPN and 11% for PNP transistors is observed. Despite the substantial decay in ß of transistors, the OA circuitry provided the retention of the operation speed and a small decrease in the offset voltage (about 1.5 mV) in the irradiation range mentioned. The circuitries of OA cascades and the experimental characteristics of the BTs and OAs are presented.