Easy Pulse Sensor (Version 1.1) Overview (Part 2)
In Part 1 of this article, we briefly discussed about the principle of Photoplethysmography (PPG) and its applications in retrieving vital information about the cardiovascular system. The Easy Pulse sensor allows you to measure the pulse rate from fingertip using the transmission mode PPG. The Easy Pulse Version 1.1 uses the HRM-2511-E sensor that fits comfortably onto fingertip. Inside the sensor there is an IR LED that illuminates the finger from one side. A photodetector placed on the opposite side and facing towards the IR LED detects the transmitted light through the finger. The little variations in the transmitted light intensity are synchronous with blood volume changes and hence with the pumping action of the heart. The on-board electronics filters out the noise from the PPG signal and amplifies the signal so that it is readable by a microcontroller. In this part, we continue our discussion of Easy Pulse Version 1.1 and analyze the output signals at various stages of instrumentation.
Easy Pulse sensor (Version 1.1)