A biosensor apparatus and method with sample type and cell volume
detection. The apparatus includes a sine wave generator to apply an AC
signal to a biosensor cell containing a sample, a current-to-voltage
converter, a phase shifter, a square wave generator, a synchronous
demodulator, and a low pass filter which yields a signal proportional to
the effective capacitance across the biosensor cell, which is
proportional to the volume of the sample. In addition, the
current-to-voltage converter yields a signal indicative of the type of
sample contained within the biosensor cell. The method includes applying
a sine wave to the biosensor cell, shifting the phase of the resultant
signal, generating a square wave synchronous with the sine wave,
demodulating the resultant signal with the square wave, and filtering the
demodulated signal to produce a signal proportional to the effective
capacitance across the biosensor cell. The biosensor apparatus and method
are capable of determining sample type and measuring glucose levels over
a wide range of sample volumes.