A method of determining a fluid or material level in a reservoir, the method comprising the steps of: providing a capacitive sensor array, comprising a lower electrode and a upper electrode; positioning the capacitive sensor array within a reservoir such that the lower electrode is submersed in the fluid or material with the fluid or material being in contact with the upper electrode, the electrodes (12, 14) being adapted such that the capacitance of each of the electrodes (12, 14) varies in accordance with both the extent of the electrode's immersion in the fluid or material and the dielectric constant of the fluid or materials; providing current operatively capable of charging a capacitor, said current being provided alternately to the lower and upper electrodes and said current being provided to the lower electrode at a higher frequency than the upper electrode; charging at least the lower and upper electrodes (12, 14) to a predetermined voltage using the provided current; the method characterised by measuring a capacitance of each electrode by measuring the amount of current respectively necessary to charge the lower and upper capacitive electrodes (12, 14) to the predetermined voltage, the current being measured over a range, and generating a digitized sensor voltage representing the capacitance of each electrode; calculating a level of fluid or material within the reservoir as a function of the capacitance of the upper electrode and the capacitance of the lower electrode; and varying the frequencies in proportion to the measured current's proximity to an upper limit to the range or in proportion to the measured current's proximity to a lower limit to the range. providing a capacitive sensor array, comprising a lower electrode and a upper electrode; positioning the capacitive sensor array within a reservoir such that the lower electrode is submersed in the fluid or material with the fluid or material being in contact with the upper electrode, the electrodes (12, 14) being adapted such that the capacitance of each of the electrodes (12, 14) varies in accordance with both the extent of the electrode's immersion in the fluid or material and the dielectric constant of the fluid or materials; providing current operatively capable of charging a capacitor, said current being provided alternately to the lower and upper electrodes and said current being provided to the lower electrode at a higher frequency than the upper electrode; charging at least the lower and upper electrodes (12, 14) to a predetermined voltage using the provided current; the method characterised by measuring a capacitance of each electrode by measuring the amount of current respectively necessary to charge the lower and upper capacitive electrodes (12, 14) to the predetermined voltage, the current being measured over a range, and generating a digitized sensor voltage representing the capacitance of each electrode; calculating a level of fluid or material within the reservoir as a function of the capacitance of the upper electrode and the capacitance of the lower electrode; and varying the frequencies in proportion to the measured current's proximity to an upper limit to the range or in proportion to the measured current's proximity to a lower limit to the range.