photoplethysmograph clitoral photoplethysmograph A small clear acrylic device that contains a light source, and a light detector. The light source illuminates the capillary bed of the clitoral tissue and the blood circulating within it. As clitoral engorgement increases, more light is reflected into the photosensitive cell of the device. The clitoral photoplethysmograph is placed by the participant between the labia minora; the light detector is oriented toward the clitoris. It can be attached to a vaginal photoplethysmograph so that both CBV and vaginal pulse amplitude (VPA) can be measured simultaneously. clitoral photoplethysmographs clitoris