Patent ID: 6973819

Claim:
A vapor sensing system, comprising: an active sensor that generates an active signal and an error sensor that generates an error signal; wherein said active sensor and said error sensor together comprise a vapor sensor, wherein said error signal is subtracted from said active signal to generate a compensated signal indicative of the presence of an ignitable vapor; an amplifier associated with said vapor sensor, wherein said amplifier subtracts said error signal from said active signal to generate said compensated signal, which is indicative of the presence of said ignitable vapor within a vicinity of an appliance associated with said vapor sensor; an output signal conditioning circuit which receives said compensated signal from said amplifier and generates a conditioned signal thereof for transmission to a microprocessor; a microprocessor for instructing said controller to shut down said appliance in response to an input of said conditioned signal to said microprocessor from said amplifier; and wherein said error sensor is surrounded by a membrane which selectively passes air and humidity, excluding ignitable gasoline vapors, to said error sensor, while protecting said error sensor from airflow, liquids, and dust.