Sometimes the machine will also record things like arm, leg, face, and pupil movement. When the test begins the investigator asks some questions like “Is your name, Bob?” or “Do you live in the United States?” When the criminal answers, investigator establish the norm graphs of his reaction. After that, the main questions will be asked. During the test or after that, the investigator checks the result. If he finds a significant change indicates that the criminal is lying. These changes could be faster heart rate, higher blood pressure, increased perspiration, moving and looking around and etc. When an experienced examiner uses a lie detector machine He can detect the lie with high accuracy. If you use the polygraph for the first time it could be a little bit hard for you to recognize the lying.

In this project, We use SHT20 to measure temperature and perspiration, ECG electrodes to measure respiration rate, A pulse sensor to measure heart rate and an Arduino board to get data and analyze them.