Biosensor apparatus and method with sample type and volume detection

A biosensor for measuring components within a sample, said biosensor comprising:

• a biosensor cell having a first conductor connection and a second conductor connection, said biosensor cell configured to receive the sample;
• a sine wave generator coupled to the first conductor connection of said biosensor cell, said sine wave generator producing an AC signal having a determined frequency;
• a current-to-voltage (I/V) converter having an input coupled to the second conductor connection of said biosensor cell and further having an output;
• a phase shifter having an input coupled to the output of said I/V converter and further having an output;
• a square wave generator producing a square wave synchronous with said AC signal;
• a synchronous demodulator having an output, a first input coupled to the output of said phase shifter, and a second input coupled to said square wave generator;
• and
• a low pass filter (LPF) having an input coupled to the output of said synchronous demodulator, said LPF producing a signal at an output proportional to an effective capacitance across said biosensor cell.

A method for measuring the effective capacitance across a biosensor cell having a first conductor connection and a second conductor connection, the biosensor cell configured for use in a biosensor to receive a sample having a volume, said method comprising the steps of:

• applying a sine wave having a determined frequency to the first conductor connection of the biosensor cell to produce an AC signal;
• shifting the phase of said AC signal;
• generating a square wave synchronous with said sine wave;
• demodulating said AC signal with said square wave to produce a demodulated signal;
• and
• filtering said demodulated signal to produce a signal proportional to the effective capacitance across the biosensor cell.

An apparatus for measuring the effective capacitance across a biosensor cell having a first conductor connection and a second conductor connection, the biosensor cell configured to receive a sample having a volume, said apparatus comprising:

• a sine wave generator having an output for coupling to the first conductor connection of the biosensor cell, said sine wave generator producing an AC signal;
• a current-to-voltage (I/V) converter having an input for coupling to the second conductor connection of the biosensor cell and further having an output;
• a phase shifter having an input coupled to the output of said I/V converter and further having an output;
• a square wave generator producing a square wave synchronous with said AC signal;
• a synchronous demodulator having an output, a first input coupled to said phase shifter, and a second input coupled to said square wave generator;
• a low pass filter (LPF) having an input coupled to the output of said synchronous demodulator, said LPF producing a signal at an output proportional to an effective capacitance across the biosensor cell;
• an analog-to-digital (A/D) converter having an analog input coupled to the output of said LPF and further having a digital output, said A/D converter converting said signal proportional to the effective capacitance across the biosensor cell from analog to digital;
• and
• a processor coupled to the digital output of said A/D converter to process said digital signal proportional to the effective capacitance across the biosensor cell to derive the effective capacitance across the biosensor cell and to derive the volume of the sample based on the effective capacitance.