Patent ID: 6856125
Filing Date: 2005-02-15
Classification: G01N,G01R

Abstract:
1. 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; 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 the biosensor cell.