Patent ID: 7490817

Claim:
A distance indicating system for an associated air spring used on an associated vehicle, the associated air spring including first and second support members secured together by an elastomeric wall such that the support members move relative to one another in response to a load applied to the associated air spring, said distance indicating system comprising: a transceiver including a first antenna and operative to broadcast an electromagnetic wave using said first antenna; and, a transponder spaced a distance from said transceiver and within the broadcasting range of said electromagnetic wave, said transponder including a second antenna adapted to receive said electromagnetic wave, and said transponder operative to shunt said second antenna for a predetermined period, the shunted said second antenna inducing an amplitude variation of said electromagnetic wave broadcasted by said transceiver, said amplitude variation increasing as the distance from said first antenna to said second antenna decreases; and one of said transceiver and said transponder supported on one of said first and second support members, wherein said distance indicating system detects and measures the amplitude variation of said broadcasted electromagnetic wave, correlates specific amplitude variations with respective distances from said transceiver first antenna to said transponder second antenna, and generates a signal representative of the respective distances.