lie detector

i e detector The principle of a lie detector may be considered welf-known: emotional states are not only betrayed by a faster heartbeat and trembling hands, but also by an increase in skin surface moisture. Because the skin becomes moist, its resistance will be lower, and jt is this that makes the lie detector react. The lie detector described here actually gives two readings: one for when a "guinea pig" is asked difficult questions and one O 9V to indicate the genera) emotional 0condition of a person. J IC], 1C2 4 9V Two bare, flexible wires wound round the fingers or the wrist can be used as receivers. That means, of course, direct contact with the circuit and this must therefore be fed from two 9 V batteries or the emotional state of the "guinea pig" may be upset by mains voltages! Each change in resistance, and therefore voltage, at the input of the 9V 0.9V 7-69 elektor july/august 1983 circuit will be amplified by op-amp indication is provided by a meter Al, which also acts...