NASA’s Langley Research Center researchers have developed a measurement acquisition system that uses magnetic fields to provide power to sensors and to acquire physical property measurements from them. Unlike traditional acquisition devices, this system has the ability to make multiple measurements of different, non-related physical properties without the constraint of a limited number of data acquisition channels. Winner of the prestigious R&D 100 award, this technology has been demonstrated with a leading aircraft landing gear manufacturer to wirelessly measure the fluid levels in landing gear shock struts. In addition to fluid level, rotation, temperature, material phase changes, proximity, position, and volume measurements have all been demonstrated.

This measurement acquisition device uses magnetic fields to power and interrogate passive inductor-capacitor sensors. The measurement acquisition system produces a series of increasing magnetic-field harmonics within a frequency range dedicated to each sensor. Faraday induction via the harmonic magnetic fields produces a current in the sensor.

Once electrically active, the sensor produces its own harmonic magnetic field as the inductor stores and releases magnetic energy. The antenna of the measurement acquisition system is switched from a transmitting to a receiving mode to acquire the magnetic-field response of the sensor. The magnetic-field response attributes of frequency, amplitude, and bandwidth of the inductor correspond to the physical property states measured by the sensor. The received response is correlated to calibration data to determine the measurement.