Capacitive continuous fluid level sensor

An apparatus for determining the level of a liquid in a vessel comprising a wall and an interior volume, the apparatus comprising;

• a first plurality of sensing electrodes disposable on or within the wall of the vessel;
• a second plurality of sensing electrodes overlying the first plurality of sensing electrodes and separated therefrom by an intervening dielectric material, each sensing electrode of the second plurality of sensing electrodes overlying and corresponding to a respective one of the first plurality of sensing electrodes;
• a shield electrode overlying the second plurality of sensing electrodes;
• and
• a controller electrically connected to each of the first plurality of sensing electrodes, to each of the second plurality of sensing electrodes, and to the shield electrode, the controller configured to:
• periodically energize the first plurality of sensing electrodes;
• periodically energize the second plurality of sensing electrodes;
• periodically energize the shield electrode;
• periodically determine first capacitances at respective ones of the first plurality of sensing electrodes;
• periodically determine second capacitances at corresponding respective ones of the second plurality of sensing electrodes;
• periodically calculate differences between the first and second capacitances;
• and output a signal indicative of the presence or absence of a liquid proximate the respective ones of the first plurality of sensing electrodes and the corresponding respective ones of the second plurality of sensing electrodes based on the differences.