Patent ID: 8044698

Claim:
A liquid level detection apparatus, comprising: a resistance plate which has a conducting pattern formed on a board, the conducting pattern including a first slide portion, a second slide portion, a plus electrode electrically connected to the first slide portion, and a minus electrode electrically connected to the second slide portion; a float which moves in accordance with a change of a liquid level; a float arm having a first end and a second end, wherein the first end is attached to the float, and the second end is pivotally supported so as to be pivotally moved in accordance with the movement of the float; a sliding arm which slides over the resistance plate in accordance with a pivotal movement of the float arm according to the liquid level; a plus connection terminal connected to the plus electrode; a minus connection terminal connected to the minus electrode; and a protective layer formed on the plus connection terminal so as to cover the plus connection terminal, wherein a potential difference developing between the plus electrode and the minus electrode corresponding to positions of the first slide portion and the second slide portion which are held in contact with the sliding arm is outputted to an external circuit via the plus connection terminal and the minus connection terminal; wherein the protective layer is a plating layer made of gold or gold alloy; and wherein the protective layer prevents the minus electrode from being subjected to deposition of a metal oxide caused by metallic ions dissolved from the plus electrode by the electrolysis; wherein the plus connection terminal is formed by applying an electrolytic corrosion-preventing treatment to a substrate to thereby cover a surface of the substrate with the protective layer and subsequently by processing the substrate into a predetermined shape, and the plus connection terminal except a cut surface thereof cut in the shaping process is covered with the protective layer; wherein the plus connection terminal has an engagement portion engaged with a frame receiving the resistance plate therein; and wherein a portion of the plus connection terminal except the engagement portion is covered with the protective layer.