Many people know the principles of this lie detector, a person’s emotional state is not only characterized by a faster heart rate but also with increased levels of water on the surface of the skin because the skin becomes watery, then the resistance is lower and this will cause the lie detector to work. This circuit diagram of the detector actually gives two readings: one for people with a trial when the question with a difficult question and one for shows the general emotional state of a person.
Two pieces of wire bending on a roll in the fingers or wrist, and in use as a receiver. to secure do not use the power flows from the house, use a 9V battery.
Any change in resistance will be reinforced by the OP-AMP A1, and also serves as a buffer, the output signal results will give a reading. The most suitable meter is a kind used in the FM receiver tuning pointer is zero in the middle. Condenser C1 warrant emphasis hum (hum) that appears.
A person’s emotional state can be determined by measuring the average resistance of the skin at a period of time. This sign is given by a meter that is connected to point B on the circuit.
Operational amplifier A2 is connected as an integrator and allows the circuit to automatically adjust the price of the average – average resistance of the skin. period duration measured resistance is determined primarily by R5, C2, C.
When the time has elapsed, the meter is connected to the output B will not give a reading, but the diodes D1 and D2 guarantee that the circuit is working as quickly as possible.
Potentiometer P1 allows a delay time of the circuit. because the resistance of the skin varies from one person to another it is necessary to change the value of R1.
Meter readings that are too high B show that the low resistance of the person who has the characteristics of people with hands moist and it is recommended to reduce the value of R1.