Low-Profile Wireless Sensor

The SansEC sensor system consists of multiple pairs of inductor-capacitor sensors with no electrical connections, which are placed throughout the material being monitored for damage. The sensors are embedded in or placed directly onto the surface of the material. Strains and breaks are detected by changes in resonant frequency read by the accompanying magnetic field data acquisition system. When pulsed by a sequence of magnetic field harmonics from the acquisition system, the sensors become electrically active and emit a wireless response. 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 physical property measurement. Because each sensor pair has its own frequency response, when damage occurs to that circuit the frequency response changes. This change identifies the damage location within the material. A unique feature achieved by eliminating electrical connections is that damage to a single point will not prevent the sensor from being powered or interrogated. If a sensor is broken, two concentric inductively coupled sensors are created, thus identifying tamper or damage location.

The technology presents a fundamental change in the way electrical devices are designed, using an open circuit in conjunction with a floating electrode, or an electrically conductive object not connected to anything by wires, and powered through a wireless device. This system uses inductor-capacitor thin-film open circuit technology. It consists of a uniquely designed, electrically conductive geometric pattern that stores energy in both electric and magnetic fields, along with a floating electrode in proximity to the open circuit. When wirelessly pulsed from the handheld data acquisition system (U.S. Patent Number 7,159,774, Magnetic Field Response Measurement Acquisition System), the system becomes electrically active and develops a capacitance between the two circuit surfaces. The result is a device that acts as a parallel plate capacitor without electrical connections.

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.

The fluid measurement sensor is configured with a spiral electrical trace on flexible substrate. The sensor receives a signal from the accompanying magnetic field data acquisition system. 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 transmitting to 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 calibrated data to determine the physical property measurement. When multiple sensors are inductively coupled, the data acquisition system only needs to activate and read one sensor to obtain measurement data from all of them. Fluid level measurement occurs in several ways. In the immersion method, the capacitance of the sensor circuit changes as it is immersed in fluid, thus changing the frequency response as the fluid level rises or falls. Fluid level can also be measured from the outside of a non-conductive container. The response frequency from the sensor is dependent upon the inductance of the container plus the combination of fluid and air inside it, which corresponds to the level of liquid inside the container. Roll and pitch are measured by using three or more sensors in a container. With any given orientation, each sensor will detect a different fluid level, thus providing the basis for calculating the fluid angle. Volume can be measured in the same way, using the angle levels detected by the sensors and the geometric characteristics of the container to perform the volume calculation.

The invention uses the superconducting "proximity effect" and/or the "inverse proximity effect" to form a spatially varying order parameter. When designed to expel magnetic flux from a region of space, the proximity effect(s) are used in concert to make the superconducting order parameter strongly superconducting in the center and more weakly superconducting toward the perimeter. The shield is then passively cooled through the superconducting transition temperature. The superconductivity first nucleates in the center of the shielding body and expels the field from that small central region by the Meissner effect. As the sample is further cooled the region of superconducting order grows, and as it grows it sweeps the magnetic flux lines outward.