Abstract An electronic circuit for measuring the psychogalvanic reflex in human beings. Two finger electrodes are connected on adjacent fingers of a person''s hand. These electrodes are part of a resistance bridge circuit which uses a transistor as an unbalance gating device. A meter indicates the bridge voltage. This meter is nulled, or the circuit balanced, by adjustment of a variable resistor. So long as the person to whom the electrodes are attached receives no exciting stimuli, the circuit will remain balanced. Should the person answer a question untruthfully, this will create sufficient stimulus to trigger the psychogalvanic reflex, thus creating a circuit unbalance due to the decrease in apparent skin resistance. This unbalance will appear as an increased transistor collector current and will cause a meter deflection, thus indicating that a particular response was not truthful.
Apparatus having automatic meter overload protection for measuring the psychogalvanic reflex in human beings comprising, in combination: a. a voltage source; b. a switch connected in series with said voltage source; c. a first resistor connected in parallel with said voltage source; d. a second resistor, connected in series with said first resistor and connected to said voltage source; e. a third resistor connected in parallel with said first and second resistors; f. a variable resistor, connected in series with said third resistor, having a variable voltage tap connection; g. a transistor with a base, a collector and an emitter, having its base connected to said variable voltage tap and its emitter connected to said voltage source; h. a fourth resistor, connected in parallel with said first and second resistors and connected to the collector of said transistor; i. a galvanometer type meter connected between the collector of said transistor and a circuit node location between said first and second resistors; j. a fifth resistor connected between the collector of said transistor and said meter; and k. electrode means for engaging the skin of a person to sense the resistance of the skin of said person and connected to form a resistance in parallel with said third resistor.
Claim 2
Dependent Claim
208 words
Apparatus having automatic meter overload protection for measuring the psychogalvanic reflex in human beings comprising, in combination: a. a voltage source; b. a switch connected in series with said voltage source; c. a first resistor connected in parallel with said voltage source; d. a second resistor, connected in series with said first resistor and connected to said voltage source; e. a third resistor connected in parallel with said first and second resistors; f. a variable resistor, connected in series with said third resistor, having a variable voltage tap connection; g. a transistor with a base, a collector and an emitter, having its base connected to said variable voltage tap and its emitter connected to said voltage source; h. a fourth resistor, connected in parallel with said first and second resistors and connected to the collector of said transistor; i. a galvanometer type meter connected between the collector of said transistor and a circuit node location between said first and second resistors; j. a fifth resistor connected between the collector of said transistor and said meter; and k. electrode means for engaging the skin of a person to sense the resistance of the skin of said person and connected to form a resistance in parallel with said third resistor.