Description
The lie detector works by measuring the galvanic reaction. In other words, when a person is lying, they tend to sweat. Sweat has a high sodium content, so sweat is conductive. A dry skin has a resistance of about 1 million ohms, while the resistance of moist skin is reduced by a factor of ten or more.
A person holding the probe cables changes the voltage at the top probe cable depending on their skin resistance. The skin resistance is parallel to R2, and since it is likely to be less than or similar to R2, the voltage on the probe wire decreases with decreasing skin resistance.
