APPARATUS FOR MEASUREMENT OF ELECTRODERMAL PHENOMENA

• US 3,556,083 A
• Filed: 05/02/1968
• Issued: 01/19/1971
• Est. Priority Date: 05/02/1968
• Status: Expired due to Term

• Current Assignee: James A. Grichnik, Joel J. Schmutzer
• Original Assignee: James A. Grichnik, Joel J. Schmutzer
• Inventors: Grichnik, James A., Schmutzer, Joel J.
• Application Number:
  US04/725,994
• Time in Patent Office: 992 Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0531 Measuring skin impedance

Abstract

An operational amplifier applies either constant voltage or constant current to a subject in order to provide an output voltage directly proportional to the subject'"'"''"'"'s conductance or resistance for recording together with superimposed sharp pulses produced by a voltage-to-time interval converter, the time interval between successive pulses being proportional to the average basal electrodermal phenomena, basal resistance or basal conductance. Means for automatically suppressing the average basal electrodermal phenomena from the signal being recorded is provided.

Claims

1. Apparatus for measuring and recording electrodermal phenomena accompanying emotional and other stresses of a subject comprising:

a pair of electrodes adapted to be connected to said subject at different sites;

means for applying a constant electrical signal to said electrodes to thereby establish a constant electrical stimulus field in the subject between said sites;

a recorder having a differential amplifier stage at the input thereof, said amplifier having first and second input terminals adapted to receive two signals the difference between which is to be amplified and recorded;

means connecting one of said electrodes to one input terminal of said differential amplifier; and

a low pass filter coupling the other one of said electrodes to the other one of said input terminals of said differential amplifier, whereby said recorder makes a record of an output voltage directly proportional to the electrodermal phenomena between said two sites with automatic suppression of a basal phenomena.

2. Apparatus as defined in claim 1 including means for temporarily reducing the time constant of said filter, whereby said recorder may be more rapidly adjusted to center its trace thereon.

3. Apparatus as defined in claim 1 including means for voltage dividing the signal coupled by said filter to the other one of said input terminals of said differential amplifier whereby a portion of said basal phenomena is added to the electrodermal phenomena signal directly connected to said one of said input terminals of said differential amplifier from said one of said electrodes.

4. Apparatus as defined in claim 1 including:

an integrator having an input and an output terminal;

means coupling said one of a said electrodes to the input terminal of said integrator;

a threshold detecting means connected to the output terminal of said integrator for resetting said integrator when the integrated signal therein reaches a predetermined level and, in response to resetting said integrator, for producing a sharp pulse; and

means for coupling said sharp pulse from said threshold detecting means to said one input terminal of said differential amplifier for recording as a sharp pulse superimposed upon the recorded electrodermal phenomena, the time interval between recorded pulses being directly proportional to the average basal phenomena present between said sites in response to said constant electrical stimulus.

5. Apparatus as defined in claim 4 including means for temporarily reducing the time constant of said filter while adjusting said recorder.

6. Apparatus as defined in claim 5 including means for voltage dividing the signal coupled by said filter to the other one of said input terminals of said differential amplifier whereby a portion of said average basal voltage is added to the electrodermal phenomena signal directly connected to said one of said input terminals of said differential amplifier from said one of said electrodes.

7. Apparatus as defined in claim 1 in which all common terminals are floating and referenced to a floating power supply in order to avoid spurious current return paths.