The objective of this work was to design and build a non-invasive probe and an amplifier for biopotential recording from characteristic points located on the body surface, considered here as small localized biosources (SLB). This non-invasive sensor aims to obtain its information without a physical penetration of the skin. To eliminate the possibility that the operator may influence the testing process through unconscious variations in pressure, the probe has an integrated pressure compensation system based on a force sensor. This system allows the operator to push the electrode of the probe on the measure point to a well defined and repetitive pressure obtaining reliable and repeatable measurements. These are virtually insensitive to fluctuations in pressure over a wide range of values and operating at all time under specified conditions. The probe can be used to detect small dc currents emitted by points of the human skin.
The specific points of interest (acupuncture points) are described in literature as being one millimeter in diameter and their electrical characteristics have been extensively studied since the 1950s to establish their existence by scientific methods -. To date, the
bioelectric properties of acupuncture points are not clearly understood but they are frequently described as having distinct electrical properties. -. These properties include increased conductance, reduced impedance and resistance, increased capacitance, and
elevated electrical potential compared to adjacent points -. This assertion has been used as a means to localize and analyze acupuncture points for diagnostic purposes . Yet, the electrical characterization of acupuncture points is associated with important technical issues that are often overlooked. Electrode polarizability, stratum corneum impedance, presence of sweat glands, choice of
contact medium, electrode geometry, and other factors contribute to the final electrodermal reading and may cause doubts about the validity of electrodiagnostic devices .