Boom height sensor systems, methods and apparatus

A liquid applicator implement for applying a liquid product to an agricultural field, comprising:

• a boom operably supported from a vehicle, the boom having a working position and a folded position, wherein in the working position, the boom extends transverse to a direction of travel of the vehicle such that the boom has a first outer end and a second outer end, each laterally outward from a centerline of the vehicle;
• a plurality of drop assemblies spaced along the boom between the first outer end and the second outer end of the boom, each of the plurality of drop assemblies including:
• a riser having an upper end and a lower end, the lower end extending downwardly from the boom toward a ground surface;
• a base unit supported at the lower end of the riser, the base unit supporting at least one tube, the at least one tube having an inlet end and an outlet end, the inlet end in fluid communication with a liquid product from a liquid source, the outlet end delivering the liquid product to the ground surface;
• wherein the base unit of at least one of the plurality of drop assemblies supports a height sensor assembly, the height sensor assembly including:
• a pivot assembly pivotally supported from the base unit about a generally vertical pivot axis;
• a ground engaging arm pivotally supported from the pivot assembly about a generally horizontal pivot axis, the ground engaging arm having a leading edge extending below the base unit and in engagement with the ground surface when the boom is in the working position, whereby as a distance between the base unit and the ground surface changes as the liquid applicator implement traverses the field, the ground engaging arm rotates about the generally horizontal axis;
• a rotation sensor disposed to detect rotational movement of the ground engaging arm about the generally horizontal axis, the rotation sensor generating a height signal indicative of a distance between the base unit and the ground surface;
• wherein, when the implement moves in a forward direction of travel, the pivot assembly pivots about the generally vertical axis such that the leading edge of the ground engaging arm is oriented toward the forward direction of travel;
• wherein, when the implement moves in a reverse in direction of travel, the pivot assembly pivots about the generally vertical axis such that the leading edge of the ground engaging arm is oriented toward the reverse direction of travel;
• a controller responsive to the generated height signal to actuate a boom height adjustment mechanism to raise the boom relative to the ground surface upon the generated height signal indicating a distance to the ground surface below the base unit is less than a predetermined distance.