Patent ID: 8181502

Claim:
A method of calibrating a measurement system operable to measure a spatial position of a meniscus of a liquid included within a container and therefrom generating a corresponding liquid content signal indicative of a proportion of the container filled with the liquid, the method including steps of: (a) from a first time instance when the container is in a first state including a first quantity of the liquid, progressively filling during a calibration phase the container with the liquid at a substantially constant volumetric rate, which rate is unknown, of liquid delivery whilst periodically simultaneously recording corresponding generated values of a meniscus position indicative signal generated by the measurement system; (b) at a second time instance after the first time instance during the calibration phase, terminating progressive filling of the container with the liquid when the position indicative signal corresponds to the container being in a second state including a second quantity of the liquid; and (c) determining the position of the meniscus at one of (a) a lower and upper position over which calibration is desired and (b) a given volumetric capacity K of the container corresponding to the meniscus being at an upper position; and (d) subsequently, in normal use after the calibration phase, applying signal processing to the position indicative signal provided from the measurement system to generate the corresponding liquid content signal indicative of the proportion of the container filled with the liquid, the signal processing accounting for the container during the calibration phase having been filled at the substantially constant volumetric rate of liquid delivery to the container.