The pulse oximeter has made a significant impact on the medical field. It is a diagnostic tool used world-wide in medicine to monitor the blood oxygen saturation as well as the heart rate. It is particularly a convenient and non-invasive measurement instrument and is very useful for monitoring patients during anesthesia, intensive care, emergency departments, general wards or those with conditions such as asthma. This book covers how to make a pulse oximeter using ADuC842 microcontroller.