Patent ID: 7863907

Claim:
A system for sensing a characteristic in a subterranean environment, comprising: a signal generator, configured and arranged to generate an electromagnetic signal; a sensor probe, locatable in a region of the subterranean environment, the sensor probe including a resonant circuit portion that includes a capacitive element, the resonant circuit portion being configured and arranged to receive energy from the electromagnetic signal and to generate a ringing signal in response to the electromagnetic signal, wherein the capacitive element of the sensor probe is responsive to a condition of the characteristic in the region of the subterranean environment to modulate the ringing signal in accordance therewith; the capacitive element comprising: a first conductor plate having a first conductive layer supported by a first substrate; and a second conductor plate having a second conductive layer supported by a second substrate, the first and second conductor plates together defining an adjustable gap therebetween, the adjustable gap being adjustable responsive to the condition to alter a capacitance of the capacitive element, wherein the adjustable gap is adjustable responsive to a temperature condition to alter the capacitance of the capacitive element; wherein the first conductive layer has a higher coefficient of thermal expansion than does the first substrate, the second conductive layer has a higher coefficient of thermal expansion than does the second substrate, and a volume between the first and second conductor plates comprising the adjustable gap being in fluid communication with the subterranean environment via a vent formed in at least one of the first conductor plate and the second conductor plate, wherein a member extending between the first and second conductor plates defines the volume, and wherein the member comprises a compressible member constructed and arranged to resiliently compress in response to flexing of the conductor plates; a receiver, configured and arranged to receive the modulated ringing signal; and a processor, configured and arranged to process the modulated ringing signal to obtain a measurement of the condition.