Abstract: A sensor and system for measuring the level of a liquid includes a linear potentiometer having a resistance circuit element and a mechanism for changing the resistance of the circuit element including a conductor formed from a semiconducting composition having a resistance inversely proportional to the horizontal force it experiences. The sensor includes an elongated vertical support structure and a float mechanism which is mounted on the support structure to move vertically therealong at the level of the liquid in a fuel storage tank. The float mechanism includes a roller which rolls along the support structure and supplies the horizontal force to the semiconducting composition. The semiconductor composition cooperates with another conductor coupled to the resistance circuit element to produce an electrical signal which is the function of the vertical position of the roller on the support structure.