In this paper, we propose a mode-localized resonant tilt sensor based on 3 degree-of-freedom (DoF) weakly coupled resonators (WCRs). The angle of rotation around the sensing axis causes gravity perturbation to the two outer resonators and influences the energy distribution of the WCRs system, finally resulting in a drastic change of the mode shape. The experimental results indicate that the sensitivity is improved by 326% compared with the 2-DoF mode-localized resonant tilt sensor. Under the closed-loop test, the resolution of the tilt sensor can achieve 2.4e-5 degrees within the range of 50 degrees.

A Mode-localized Tilt Sensor with Resolution of 2.4e-5 Degrees within the Range of 50 Degrees

High-altitude electric fields are a critical parameter of electricity in the atmosphere. Due to such drawbacks as their bulk and high cost, traditional electric field mills are not available for daily atmospheric sounding purposes. This paper introduces a highly sensitive and robust electric field sounding sensor based on an existent micro-electro-mechanical systems chip and a new protective package that augments sensor sensitivity. To gain high sensitivity, an innovative external metal electrode connects to the electric field microchip’s package cap, hangs down out of the guardian foam, and effectively enhances the local electric field near the microchip due to the distortion effect. This distortion regularity was studied during a series of finite element simulations, calibrations, and comparison experiments. With a 1.5-meter-long external electrode, the sensitivity of the sensor reached 465 mV/kV/m with a resolution that was better than 10 V/m in an actual long-term ground comparison test. Furthermore, the microsensor chip and its circuit are protected inside a foam while the metal electrode is exposed outside, therefore gaining a robust stability during harsh environments such as low temperature, rainfall, etc. To examine the performances, we built an electric field sounding system, including the electric field sensor, a radiosonde, and a receiving antenna, and measured high-altitude electric fields in various weather conditions. Intended for atmospheric electricity research, our innovative electric field sounding sensor would be especially propitious if integrated with a radiosonde and applicable to daily sounding services.

Toward Atmospheric Electricity Research: A Low-Cost, Highly Sensitive and Robust Balloon-Borne Electric Field Sounding Sensor

Abstract This paper outlines the design of a novel mode-localized electric current sensor based on a mechanically sensitive element of weakly coupled resonator systems. With the advantage of a high voltage sensitivity of weakly coupled resonator systems, the current under test is converted to voltage via a silicon shunt resistor, which causes stiffness perturbation to one resonator. The mode-localization phenomenon alters the energy distribution in the weakly coupled resonator system. A theoretical model of current sensing is established, and the performance of the current sensor is determined: the sensitivity of the electric current sensor is 567/A, the noise floor is 69.3 nA/√Hz, the resolution is 183.6 nA, and the bias instability is 81.6 nA. The mode-localized electric current sensor provides a new approach for measuring sub-microampere currents for applications in nuclear physics, including for photocurrent signals and transistor leakage currents. It could also become a key component of a portable mode-localized multimeter when combined with a mode-localized voltmeter. In addition, it has the potential for use in studying sensor arrays to achieve higher resolution. 

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Micromechanical mode-localized electric current sensor

This paper reports a mode-localized magnetometer with novel 3 degrees-of-freedom (DOF) weakly coupled resonators (WCRs) coupled by F-shaped coupling beams. In this coupling mechanism, the direct coupling between the two outer resonators can be effectively suppressed, which decreases the coupling coefficient and drastically increases the sensitivity. Utilizing these novel WCRs for Lorentz force sensing, a magnetometer is realized with the resolution of $6.9\ \text{nT}/\surd \text{Hz}$ in the range of 100 mT, which is an improvement of 234.78 times that of state-of-the-art mode-localized magnetometers ( $1.62\ \mu \mathrm{T}/\surd\text{Hz}$ ).

A Mode-Localized Magnetometer with Resolution of $6.9\ \text{NT}/ \surd \text{Hz}$ Within the Range of 100 mT

To improve the sensitivity and stability, a novel mode-localization resonant MEMS (Micro-Electro-Mechanical System) electric field sensor based on closed-loop feedback is presented in this paper. The sensor is based on the principle that the mode localization effect can dramatically increase the sensitivity of a resonant system. Moreover, in order to detect the electric field in real-time and improve the resolution and stability of the sensor, closed-loop feedback is introduced. One of the output signals of the sensor is fed back to the input port, where the output signal has been processed by a phase-locked loop part and automatic gain control part. This paper analyzes amplitude-frequency characteristics, phase-frequency characteristics, sensitivity, and output characteristics by modeling, theoretical calculation, and finite element simulation. The device prototype is fabricated based on SOI process. Tested in vacuum conditions, the minimum detectable electrostatic field of the sensor is better than 10V/m, the accuracy of the sensor is 5.3%, and the repeatability is 0.56%.

Enhanced Sensitivity and Stability of a Novel Resonant MEMS Electric Field Sensor Based on Closed-Loop Feedback

This paper for the first time reports a resonant DC electric field sensor (EFS) based on the mode localization phenomenon. The sensor uses a 3-degrees-of-freedom (DoF) weakly coupled resonator (WCR) as the mechanical sensing element, with comb capacitors on both sides for converting electric field to stiffness perturbation. The perturbation causes a drastic change in the mode shape owing to the mode localization phenomenon. Then we use the amplitude ratio (AR) instead of the frequency as the readout metric, and the sensitivity based on the AR is 1720 times higher than that based on the frequency. Just under the open-loop test, the resolution of the sensor reaches 20.4V/m√ Hz in the range of 7 kV.

A Micro Resonant DC Electric Field Sensor Based on Mode Localization Phenomenon

This paper for the first time reports a resonant magnetometer based on the mode localization phenomenon. The proposed sensor utilizes a 3 degrees-of-freedom (DoF) weakly coupled resonators (WCRs) as the mechanical sensing element, with massive grill structures on both sides for converting magnetic field strength to stiffness perturbation. Stiffness perturbation will cause a drastic variation in the mode shape owing to the mode localization phenomenon. We use the amplitude ratio (AR) instead of the frequency as the readout metric, and the sensitivity of AR is 7800 times higher than that of frequency. And the best resolution of the magnetometer is 1.6μT/√Hz in the range of 90mT.

A Mode-Localized Lorentz Force Magnetometer with 1.6μT/√Hz Resolution

The invention belongs to the field of MEMS (microelectrochemical systems) and relates to a weak electrostatic field measuring device and method based on weak coupling micromechanical resonators. An electric field intensity measuring chip includes a plurality of resonators serially connected through a mechanical coupling beam, a voltage input electrode, detection electrodes and a driving electrode;the resonators are weakly coupled via a bridge beam; the bridge coupling beam designed herein helps relieve axial stress generated during processing, and it is ensured that a device is not affected by residual stress. Output signals of both two resonators are detected and guided out by two detection electrode units for differentiation, signal intensity is enhanced, feed-through capacitance signalinterference due to a potential difference between the driving electrode and the detection electrodes is eliminated, and stability and accuracy of measuring signals are greatly improved. Large-scalecomb booth arrays are arranged on the two sides of the resonators herein and are available to sensitive electric fields under detection; the intensity of the electric fields under detection can be measured more sensitively; ultrahigh-precision electrostatic field measurement and environmental noise suppression are guaranteed.

Weak electrostatic field measuring device and method based on weak coupling micromechanical resonators

The invention discloses a high-sensitivity voltage measuring method and device, belonging to the field of electronic measuring instruments. The device comprises at least two voltage measuring chips and a signal processing circuit. The device further comprises weak coupling resonators connected through a mechanical coupling beam and through electrostatic coupling, a voltage input electrode, detection electrodes and a drive electrode. The input of the voltage signals change the static negative stiffness formed by the voltage input electrode and the resonators so as to change the total stiffnessof a weak coupling resonator system, the change of the stiffness of the resonator system can generate sharp balance of the energy distribution of the resonators, the amplitude ratio of the two resonators as output are sharply changed so that the amplitude ratio of the two resonators are taken as output to achieve the voltage measurement with super-high sensitivity; the two resonators as output areprovided with two sets of detection electrodes to achieve differential detection for the amplitude of a single resonator so as to enhance the intensity of the signals, eliminate the feed-through capacitance signal interference caused by potential difference between the drive electrode and the detection electrodes and greatly improve the stability and accuracy of measurement signals. The measurement method based on a resonant-mode voltage meter can perform continuous measurement for the voltage signals to be measured in real time and has a high anti-interference ability so as to make up the defects that a digital voltmeter is not continuous in display and poor in anti-interference ability.

Yan Zimu

Papers

A Micro Resonant DC Electric Field Sensor Based on Mode Localization Phenomenon

A Mode-Localized Lorentz Force Magnetometer with 1.6μT/√Hz Resolution

Weak electrostatic field measuring device and method based on weak coupling micromechanical resonators

High-sensitivity voltage measuring device and method based on weak coupling micromechanical resonator