How Lie Detectors Work

For more than 15 years, Robert Hanssen led a double life. In one life he was a 25-year veteran with the Federal Bureau of Investigation (FBI) who had access to some of the nation most-classified information.

Lie Detector

This circuit is based on the fact that a person skin resistance changes when they sweat (sweating because they are lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.

Simple Lie Detector

Here is a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

Lie detector

simple circuit.

Lie detector

Simple lie detector