Patent ID: 8691152

Claim:
An apparatus for determining the concentration of a medically significant component of a biological fluid, the apparatus comprising: a cell for receiving a sample of a biological fluid containing a medically significant component, the cell supporting: a chemistry which reacts with the medically significant component; and first and second terminals across which the reaction of the chemistry with the medically significant component can be assessed; an instrument having: first and second terminals complementary to the first and second terminals, respectively, of the cell; wherein placement of the first and second terminals of the cell in contact with the first and second terminals, respectively, of the instrument permits the instrument to assess the reaction; and an assessment controller for: applying across the first and second terminals of the instrument a first signal having an AC component comprising an amplitude not more than about 56.6 mV and comprising at least 2 and not more than 10 different frequencies applied generally serially wherein the highest and lowest frequencies are at least an order of magnitude apart; determining a first correction value in response of the cell to the first signal wherein said response comprises measurements of response of the cell at each different frequency of the first signal, said measurements taken by the instrument at regular intervals; assessing the reaction of the medically significant component with the chemistry; and combining the correction value with the result of the reaction assessment to produce an indication of the concentration of the medically significant component of the sample.