Patent ID: 8121676
Filing Date: 2012-02-21
Classification: A61B

Abstract:
1. A device operated by a user to monitor and indicate changes in resistance of a living body comprising: a resistance measuring circuit having external leads for sensing the resistance of a living body placed across the external leads; an amplifier coupled to the resistance measuring circuit for producing an analog measurement signal indicative of the sensed body resistance; an indicator circuit for displaying visually perceivable indicia representative of sensed body resistance changes; and a digital processing unit for digitizing and digitally processing the analog measurement signal in a manner that substantially offsets effects of component aging, tolerances and temperature on measurement signal accuracy wherein the digital processing unit includes means for substituting a plurality of electrical resistance values for sensing by the amplifier in lieu of a body resistance to produce measurement signals corresponding to simulated body resistance values, said plurality simulating a plurality of body resistance values, means for digitizing the measurement signals corresponding to the simulated body resistance values, and storing in memory a resulting plurality of calibrated measurement values corresponding to the plurality of simulated body resistance values, compensation means for computing, based on the stored calibrated measurement values, calibrated measurement values to be associated with respective additional body resistance values, means for producing an indicator-driving series of digital difference values during the monitoring of the living body's resistance that represent a difference between the monitored living body's digitized measurement signals and a selected user-adjustable base value, the user-adjustable base value being selected by the user from calibrated measurement values, manually positionable means operable by the user to select from the plurality of said base values, and sensitivity adjustment means for controlling a change in the indicator-driving difference values caused by a change in the monitored living body's sensed resistance, and means applying an automatic correcting gain factor to the indicator-driving value as a function of the selected base value to produce the digitally processed measurement signal, the gain-applying means applying a first non-linear gain when the selected base value corresponds to a low living body resistance value of less than approximately 5 K-ohms, and a second non-linear gain when the selected base value corresponds to a high living body resistance value of more than 100 K-ohms, the gain for the living body resistances values therebetween being essentially a constant, said first non-linear gain being more than said constant and increasing with decreasing base value, said second non-linear gain being less than said constant and increasing with increasing base value.