• Light • Light Sensors • Photoemissive Sensors • Photovoltaic Sensors • Photoconductive Cells • Photodiodes and Phototransistors • Electro-Optics Instrumentation • Photoplethysmography (PPG) • Blood Oxygen Measurement PPG • What is impedance? • Series-parallel equivalent circuits • Impedance measurement • Some applications • -- Galvanic skin resistance (GSR) • -- Impedance pneumotachometry • -- Impedance-based cardiac output measurement • -- Electrical impedance tomography (EIT) • -- Others