Electric field sensor
Inventors
Ghionea, Simon J. • Hull, David M. • Smith, Gabriel L. • Pulskamp, Jeffrey S. • BEDAIR, SARAH S.
Assignees
United States Department of the Army
Publication Number
US-9880120-B2
Publication Date
2018-01-30
Expiration Date
2034-07-22
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Abstract
According to embodiments, an electric field sensor having a sensor electrode is constructed of an electrically conductive material and having one or more outwardly protruding pillars. A screen electrode overlies the sensor electrode and has one or more openings which register with the one or more pillars on the sensor electrode. At least one piezoelectric actuator is connected to the screen electrode so that, when excited by a voltage signal, the piezoelectric actuator modulates the screen electrode toward and away from the sensor electrode at the frequency of the periodic voltage signal. An output circuit configured to detect a voltage, a current output, or both, between the sensor electrode and the screen electrode which is proportional in magnitude to the strength of the electric field.
Core Innovation
The invention provides an electric field sensor comprising a sensor electrode constructed of an electrically conductive material with one or more protruding pillars, and a screen electrode overlying the sensor electrode with openings registered to the pillars. The screen electrode is movable relative to the sensor electrode by at least one piezoelectric actuator that modulates the screen electrode toward and away from the sensor electrode at a frequency driven by a periodic voltage signal. The sensor includes an output circuit configured to detect a voltage or current output proportional to the strength of an external electric field.
The problem addressed involves limitations in prior art low frequency electric field sensors, including the complexity, size, and power consumption of mechanical field mills, the susceptibility of D-Dot sensors to common mode interference signals, and the challenges in MEMS electric field sensor technology related to interference from electrostatic drive electronics and power consumption from thermal drives. The present invention overcomes these disadvantages by using piezoelectric actuators to enable low-voltage operation, low power consumption, and improved sensitivity while minimizing common mode noise through differential resonance modes.
The invention further discloses multiple embodiments including one in which the screen electrode modulates translationally relative to sensor electrodes with pillars, and another where sensor and screen electrodes have interdigitated fingers that tilt oppositely driven by piezoelectric actuators. The modulating screen electrode periodically screens and exposes the sensor electrode to the ambient electric field thereby modulating the current output proportionally to the electric field strength. Differential resonance at certain frequencies enhances output signals and reduces common mode noise through sensor electrode subdivision and separate outputs combined to increase signal-to-noise ratio.
Claims Coverage
The patent contains multiple independent claims outlining key inventive features of the electric field sensor.
Electric field sensor with modulating screen electrode and pillars
A sensor electrode having one or more conductive pillars extending from a base, with a screen electrode overlying it having openings registered to the pillars. At least one piezoelectric actuator moves the screen electrode relative to the sensor electrode, modulating exposure to the electric field. The sensor includes an output circuit detecting voltage or current between the electrodes proportional to the electric field strength. The pillars extend higher than the screen electrode thickness, and the openings fully surround the pillars.
Electric field sensor with screen electrode position modulation
The screen electrode moves between an upper position fully above the pillars where it blocks the electric field thereby minimizing current output, and a lower position where pillars extend above the screen electrode thereby maximizing current output from the sensor electrode.
Method of operating the electric field sensor via voltage-driven modulation
Operating the sensor by applying a periodic voltage signal to the piezoelectric actuator(s) to modulate the screen electrode toward and away from the sensor electrode at the frequency of the voltage signal.
The patent claims focus on electric field sensors that utilize piezoelectric-actuated screen electrodes with openings registered to sensor electrode pillars, enabling modulation of exposure to electric fields and corresponding output signals. It also claims operation methods involving periodic voltage excitation of the actuators to achieve this modulation.
Stated Advantages
Operation at low voltages allowing easier integration with low-power sensor circuits.
Lower power consumption compared to thermal drive techniques.
Reduced interference and drive fields since actuation fields are contained within the piezoelectric material.
Capability to achieve high sensitivity and small size suitable for mobile applications and sensor arrays.
Differential resonance operation doubles output signals while effectively eliminating common mode noise, improving signal-to-noise ratio.
Documented Applications
Industrial, medical, scientific, and military uses measuring electrostatically charged particles, atmospheric electricity, brainwaves, printed circuit components, and power lines.
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