Methods and apparatus for analyte concentration monitoring using harmonic relationships

A method of electronically probing an oxidation-reduction reaction in an analyte-containing fluid, comprising:

• applying, by a first circuit, a periodic excitation signal to the analyte-containing fluid, wherein the periodic excitation signal has a fundamental frequency;
• generating, by a second circuit while the first circuit is applying the periodic excitation signal, a current measurement signal, wherein the current measurement signal has a magnitude indicative of a current produced by an oxidation-reduction reaction in the analyte-containing fluid, the magnitude dependent, at least in part, on an analyte concentration in the analyte-containing fluid;
• sampling, by a third circuit, the current measurement signal;
• providing, by the third circuit, digitized time-domain sample data representative of the current measurement signal;
• extracting a plurality of harmonic signals based, at least in part, on the digitized time-domain sample data, wherein the harmonic signals are harmonics of the fundamental frequency, and each harmonic signal has a corresponding strength;
• calculating a set of harmonic relationships based on at least a portion of the plurality of harmonic signals;
• accessing a harmonic relationship database, wherein the harmonic relationship database includes a plurality of sets of harmonic relationships, each set of harmonic relationships associated with a corresponding analyte concentration;
• and
• determining, based on the harmonic relationship database and the calculated set of harmonic relationships, a magnitude of the analyte concentration in the analyte-containing fluid.