Patent ID: 7336164

Claim:
A tire pressure monitoring system tire pressure sensor comprising a sensor circuit comprising an antenna coil, a first capacitor, a second capacitor, a pressure switch comprising a pressure membrane supported so that a first side of the membrane is positioned for exposure to the ambient pressure inside of the tire when mounted therewith, said pressure membrane having a snap action in moving from a first state to a second state when a first pressure threshold on one side of it is reached and a snap action in moving from the second state to the first state when a second pressure threshold on one side of it is reached and wherein the second pressure threshold is at least five percent greater or less than the first pressure threshold and means operable to electrically connect said second capacitor in parallel with said first capacitor in said sensor circuit when said membrane is in said second state so that said circuit will have a first resonant frequency and means operable to electrically disconnect said second capacitor from said sensor circuit when said membrane is in said first state so that said sensor circuit has a second resonant frequency that is different than said first resonant frequency.