Skin Resistance Electrode for Classroom Use

Abstract

Consideration of a skin resistance electrode appropriate for classroom use suggests a dry electrode which the student can place on his non-writing hand. Two such designs available commercially were rejected, as were 13 electrodes designed specifically for classroom use as part of this research project. The model currently in use consists of a dry stainless steel electrode held in a plastic ring, two of which the student places on the first and third fingers of his non-writing hand. Since the unit tends to be self-adjusting, movement artifacts are minimized. The two electrodes and the body electrolytes comprise a cell. One source of error is the random potential of this cell in the absence of an externally applied voltage source. This potential is less than 1% of the full-scale signal level, making this an acceptable error. A second source of error is the back EMF of the cell when it is subjected to an externally applied voltage source. This error is handled by recording the back EMF, then subtracting it from the signal during the analysis phase.