Wirelessly Interrogated Position or Displacement Sensors

Two simple position or displacement sensors based on inductance-capacitance resonant circuits have been conceived. These sensors are both powered and interrogated without use of wires and without making contact with other objects. Instead, excitation and interrogation are accomplished by means of a magnetic- field- response recorder — an apparatus previously reported in “Magnetic- Field-Response Measurement-Acquisition System” (LAR- 16908), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. To recapitulate: The magnetic-field-response recorder generates an alternating magnetic field that excites oscillations in the resonant circuit, measures the magnetic response of the circuit, and determines the resonance frequency from the response.