Activity and respiration monitor

Claim 1

Apparatus for monitoring a condition of the body of a human or animal by sensing the breathing movements of said body, comprising in combination: a resilient pad for supporting a substantial portion of the weight of said body and including a capacitor having a plurality of electrodes including a driven electrode, a receptor electrode and a dielectric layer of elastomer foam separating said electrodes to permit one of said electrodes to move toward and away from the other electrode to cause relatively long term changes in capacitance between the electrodes in response to activity of the body and relatively short term changes in capacitance between the electrodes in response to said breathing movements; and an electronic sensing circuit including (a) means connected to said driven electrode for applying an A.C. drive signal at a frequency that is high enough to be non-hazardous at the voltage levels in use, (b) an amplifier connected to said receptor electrode so that changes in capacitance modulate the output of said amplifier, (c) a demodulator coupled to said amplifier to demodulate the output thereof to produce a fluctuating D.C. signal having fluctuations representative of the changes in capacitance between said electrodes, and (d) high pass filter means coupled to said demodulator for substantially rejecting changes in said D.C. signal representative of relatively long term changes in said capacitance, said sensing circuit being operable to convert said short term capacitance changes to a D.C. output signal representative of said breathing movements.