Patent ID: 8884771

Claim:
A smoke detector using an air dielectric capacitor as a smoke sensor, said smoke detector comprising: an air dielectric capacitor having a plurality of plates, wherein the plates are arranged such that an inter-digital structure is formed between the plates, wherein when clean air flows over surfaces of the inter-digital structure the air dielectric capacitor has a first capacitance value and when smoke is in the air flowing over the inter-digital structure the air dielectric capacitor has a second capacitance value; a capacitance measurement circuit coupled to the air dielectric capacitor, wherein the capacitance measurement circuit measures a capacitance value of the air dielectric capacitor; and an alarm circuit coupled to the capacitance measurement circuit, wherein when the measured capacitance value is at substantially the second capacitance value the alarm circuit is actuated by the capacitance measurement circuit, and when the measured capacitance value is at substantially the first capacitance value the alarm circuit is not actuated.