Patent Document ID: 5541580
Application ID: 08512985
Patent Flag: 1

Claim One:
1. A method for detecting the absence of a body, said method comprising steps of: measuring a first dielectric constant of a region within which said body should reside; generating a baseline value in response to said first dielectric constant, said baseline value corresponding to a baseline dielectric constant; retaining said baseline value in a memory; measuring a second dielectric constant of said region within which said body should reside, wherein said measuring steps are carried out by a self-contained, portable unit comprising an item of wrist apparel having a circuit housing and a strap and said self-contained, portable unit comprises a capacitor including a first electrode disposed on said housing and a second electrode disposed on said strap; and evaluating said second dielectric constant measurement and said baseline value from said memory to determine whether said second dielectric constant is less than said baseline dielectric constant; wherein said measuring steps comprise steps of: producing a signal exhibiting a parameter responsive to a current capacitance of said capacitor by an oscillator coupled to said capacitor, said signal oscillating at a frequency that varies in response to said current capacitance, said current capacitance corresponding to said second dielectric constant; and generating a clocking signal by a clocking circuit, wherein a first counter is coupled to said clocking circuit and to said oscillator and wherein said first counter is configured to count said clock signal for a duration controlled by said signal produced by said oscillator to provide a control value; and wherein said retaining step includes a step of recording said control value in a memory, said memory comprising a second counter having a clock input coupled to said clocking circuit, a terminal count output and a load input, said load input coupled to said terminal count output; and wherein said evaluating step includes steps of: determining, by a threshold detector coupled to said oscillator and said memory, when: (i) said current capacitance is less than said baseline value by at least a first predetermined threshold value; (ii) said current capacitance exhibited by said capacitor is greater than said baseline value by at least a second predetermined threshold value; (iii) said current capacitance is less than a predetermined minimum capacitance; and (iv) said current capacitance is greater than a predetermined maximum capacitance, said threshold detector being configured to count oscillations of said signal for a duration determined in response to said control value; replacing said control value recorded in said memory with a new control value via an up/down counter having a clock input coupled to said terminal count output, an up/down input coupled to a most significant bit of a data output of said first counter and having a data output coupled to a data input of said second counter; and communicating an alarm when said current capacitance is less than said baseline value.