Multichannel module characterization of optical sensors employed in photoplethysmography

Pholotoplethysmography (PPG) is a medical technique using optoelectronic technology to measure blood volume changes in vessels and assess medical condition. The simultaneous multisite PPG measurement has many advantages in assessing various physiological and pathological events related to cardiovascular system. The sensor has a key role in converting the biological signal into electric signal. It mainly comprises of the light emitter and light detector within the preferred red-infrared spectrum. These sensor components have property variations even for identical ones fabricated from the same wafer and in turn may influence the multisite PPG measurement. Different ear and finger sensor pairs with components having specific requirements were considered for the multichannel setup to examine and address the optoelectronic variations. In accordance with that, the designated multichannel sensor module (MCSM) has been developed to connect and power on multiple sensors. It was specified to align intensity variations of the light emitters, reduce their effects and configure almost equivalent conditions in sensor pairs.