Impedance characteristic circuit for electrochemical sensor

A method of determining usability of an electrochemical sensor by determining an impedance associated with the electrochemical sensor, the method including:

• delivering a differential time-varying AC excitation signal component to first and second amplifier input nodes for driving an excitation signal into the sensor during a sensor impedance test;
• separately delivering a differential stable bias signal component to the first and second amplifier input nodes for biasing the first and second amplifier input nodes while driving the excitation signal into the sensor during the sensor impedance test;
• communicating a differential feedback signal from the sensor to the first and second amplifier input nodes while driving the excitation signal into the sensor;
• and
• measuring a response from the sensor while driving the excitation signal into the sensor during the sensor impedance test.

An impedance characteristic sensor interface circuit for independently delivering a differential stable bias signal component and a differential time-varying AC excitation signal component for testing an impedance of an electrochemical sensor, the sensor interface circuit including:

• an impedance excitation amplifier circuit, including:
• a first digital-to-analog converter (DAC) circuit, to convert a first digital input signal into a first analog signal for providing the differential time-varying AC excitation signal component during a sensor impedance testing mode;
• a second DAC circuit, to convert a second digital input signal into a second analog signal for providing the differential stable bias signal component during the sensor impedance testing mode;
• and
• a sensor response amplifier circuit, coupled to the sensor for receiving a response signal to the differential time-varying AC excitation signal component, during the sensor impedance testing mode.