Back to Polygraph Information Bibliography for Polygraph Information
KidZone Science
The Polygraph Machine
The polygraph machine uses the following components in order to
collect results on the subject’s reactions to questions related to
the investigation:
Blood Pressure Cuff – measures the
subject’s blood pressure, heart rate and blood volume, also known as
their cardiovascular activity. It is attached to the subject’s arm,
around their brachial artery.
Pneumograph – this is a device
that measures the respiratory activity (breathing patterns) of the
subject. A pneumograph is essentially a convoluted rubber tube; it
uses ohms law to determine how much resistance there is in the chest
cavity because there is more resistance in your chest when your
lungs are filled with air. During the polygraph test, two
pneumographs are attached to the subject, one around their chest and
the other around their abdominal area.
GSR – the galvanic
skin response is a protruding electrode which is used to determine
the changes in a subject’s anxiety. An increase in anxiety will
result in a decrease of the electrical resistance in the skin. The
galvanometer measures the small differences in electrical resistance
and any shifts in a subject’s anxiety. The polygraph test uses two
galvanometers, which are attached to two of the subject’s fingers in
order to obtain results from their electro dermal activity.