Abstract: A circuit for measuring body impedance comprising a voltage source having a predetermined frequency and a current source; a first pair of electrodes adapted to receive one portion of the body for applying said current source to said body; a second pair of electrodes adapted to receive another portion of the body for sensing a voltage therebetween; a comparator having first and second inputs and an output for producing an output signal based on signals applied to said first and second inputs; an instrumentation amplifier arrangement coupled to one of said comparator inputs and responsive to the voltage across the second pair of electrodes for providing an input signal to said first comparator input; a variable resistor coupled to the second input of said comparator and responsive to said voltage source for developing a first voltage signal applied to said second comparator input; and a processor responsive to the output signal of the comparator for controlling the resistance of the variable resistor to cause a

Abstract: The present weight scale performs automated self calibration by periodically initiating a measurement operation to determine the zero offset from a true weight reading due the weight scale's intrinsic weight. The weight scale's intrinsic weight will vary due to changes in environmental conditions such as temperature and humidity, which impact the behavior of the internal electronics that perform the weight measurement operations. The automated self calibration is provided by a counter circuit, clocked by a low power oscillator, that periodically initiates the weight scale's electronics to undertake a weight measurement of the tare weight value of the scale. The tare weight value is stored in memory until replaced by a subsequent tare weight value calculation. During a weight measurement operation the gross weight measurement is deducted by the tare weight value stored in memory to arrive at a net weight representing a user's true weight.