APPARATUS FOR DETECTING HYDROCARBONS USING CRYSTAL OSCILLATORS WITHIN FUEL DISPENSERS

摘要

A vapor recovery system (18) utilizes a crystal oscillator (30) for sensing the presence of hydrocarbon in the vapor emissions emanating from a fuel tank (10) during refueling. The crystal oscillator (30) is coate d with a layer of material having a sensitivity for hydrocarbon. In response to any interaction between the coating layer and hydrocarbon, th e crystal oscillator (30) experiences a shift in its oscillation frequency relative to the fundamental resonance frequency. The frequency shi ft (34) is representative of the hydrocarbon concentration in the vapor emissions. A control signal (36) based on the frequency shift (34) is generated and then used to adjust the operating speed of a vapor pump (26).