scholarly journals High Sensitivity Torsion Balance Tests for LISA Proof Mass Modeling

2006 ◽  
Author(s):  
S. Schlamminger ◽  
C. A. Hagedorn ◽  
M. G. Famulare ◽  
S. E. Pollack ◽  
J. H. Gundlach
Keyword(s):  
Proof Mass ◽  
High Sensitivity ◽  
Torsion Balance ◽  
Balance Tests

Usefulness of some current balance tests for identifying individuals with disequilibrium due to vestibular impairments

2009 ◽  
Vol 18 (5-6) ◽  
pp. 295-303
Author(s):  
Helen S. Cohen ◽  
Kay T. Kimball
Keyword(s):  
Sensitivity And Specificity ◽  
Care Center ◽  
Tertiary Care ◽  
High Sensitivity ◽  
Community Dwelling ◽  
Functional Mobility ◽  
Vestibular Disorders ◽  
Timed Up And Go ◽  
Balance Tests ◽  
Walking Balance

The goal of this study was to determine which of several clinical balance tests best identifies patients with vestibular disorders. We compared the scores of normals and patients on the Berg Balance Scale (Berg), Dynamic Gait Index (DGI), Timed Up and Go (TUG), Computerized Dynamic Posturography Sensory Organization Test (SOT), and a new obstacle avoidance test: the Functional Mobility Test (FMT). The study was performed in an out-patient balance laboratory at a tertiary care center. Subjects were 40 normal adults, and 40 adults with vestibular impairments. The main outcome measures were the sensitivity of tests to patients and specificity to normals. When adjusted for age the Berg, TUG, DGI and FMT had moderate sensitivity and specificity. SOT had moderately high sensitivity and specificity. SOT and FMT, combined, had high sensitivity and moderate specificity. Therefore, the kinds of tests of standing and walking balance that clinicians may use to screen patients for falling are not as good for screening for vestibular disorders as SOT. SOT combined with FMT is better. When screening patients for vestibular disorders, when objective diagnostic tests of the vestibular system, itself, are unavailable, tests of both standing and walking balance, together, give the most information about community-dwelling patients. These tests may also indicate the presence of sub-clinical balance problems in community-dwelling, asymptomatic adults.

scholarly journals DEVELOPMENT OF A HIGH-SENSITIVITY TORSION BALANCE TO INVESTIGATE THE THERMAL CASIMIR FORCE

2012 ◽  
Vol 14 ◽  
pp. 337-346 ◽  
Author(s):  
TODD GRAVESON ◽  
CHARLES RACKSON ◽  
WOO-JOONG KIM
Keyword(s):  
Casimir Force ◽  
High Sensitivity ◽  
Torsion Balance ◽  
Surface Patch ◽  
Experimental Investigations ◽  
Electric Force ◽  
Force Measurements ◽  
Semiconducting Materials ◽  
Proper Understanding ◽  
Actual Contribution

We report development of a high-sensitivity torsion balance to measure the thermal Casimir force. Special emphasis is placed on experimental investigations of a possible surface electric force originating from surface patch potentials that have been recently noticed by several experimental groups. By gaining a proper understanding of the actual contribution of the surface electric force in real materials, we aim to undertake precision force measurements to resolve the Casimir force at finite temperature in real metals, as well as in other semiconducting materials, such as graphene.

Design and Analysis of Thermal-Bubble-Based Micromachined Accelerometer

Volume 3 ◽  
2004 ◽  
Author(s):  
Ke-Min Liao ◽  
Rongshun Chen ◽  
Bruce C. S. Chou
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Velocity Field ◽  
Numerical Simulations ◽  
Frequency Response ◽  
Proof Mass ◽  
Flow Behavior ◽  
High Sensitivity ◽  
The Other ◽  
High Flux

In this study, a novel thermal-bubble-based micromachined accelerometer with advantages of no proof mass, preferable frequency response, and high sensitivity is presented. Unlike the other techniques, the only moving element in the proposed device is a small thermal-bubble created by using a high flux heater to vaporize the liquid contained in the micro chamber. In order to improve the performance of the accelerometer, the basic physical characteristics of this sensor have been analyzed. Numerical simulations are conducted to study the heat transfer and fluid flow behavior of the device and to demonstrate the feasibility of our design. The temperature profile and the velocity field distribution under different applied acceleration have been acquired. Moreover, a method for manufacturing the accelerometer by using the techniques of micromachining is provided and the performance of the presented design has been examined. The results concluded that the proposed design has better response and sensitivity comparing to its counterparts.

A MOEMS Accelerometer Based on Diffraction Grating with Improved Mechanical Structure

2015 ◽  
Vol 9 (5) ◽  
pp. 473-481 ◽  
Author(s):  
Qianbo Lu ◽  
◽  
Wenxiu Lian ◽  
Shuqi Lou ◽  
Chen Wang ◽  
...  
Keyword(s):  
Phase Modulation ◽  
Proof Mass ◽  
High Sensitivity ◽  
Bulk Silicon ◽  
Coherent Light ◽  
Theory Analysis ◽  
Transparent Substrate ◽  
Interference Fringes ◽  
Reflective Mirror ◽  
Processing Circuit

In this study, an improved MOEMS (micro-optical electronic mechanical system) accelerometer based on integrated grating with phase modulation is proposed. This device is composed of a laser diode, an optoelectronic processing circuit, a sensing chip (consisting of a piezoelectric translator), an integrated grating as a reflective mirror on a transparent substrate, and a mechanical part of a bulk silicon proof mass suspended by four cantilevers whose upper surface acted as another mirror. This device generates a series of interference fringes by two diffracted beams when illuminated with a coherent light source, whose intensities are modulated by the relative distance between the grating and the proof mass. The intensities of the interference fringes varied with alterations in the distance caused by external accelerations that are proportional to the acceleration. The magnitude of acceleration can be calculated by using a differential circuit detecting the distance. The modified structure introduced in this paper obtains high sensitivity and reduces cross-sensitivity between different sensitive axes. The experimental results before the simulation and theory analysis demonstrate that this modified MOEMS accelerometer has a good performance with higher static acceleration sensitivity of 3 x 310V/g and very low crosstalk.

A High-Sensitivity, Low-Drift MEMS Relative Gravimeter for Multi-Pixel Imaging Applications

2020 ◽  
Author(s):  
Abhinav Prasad ◽  
Karl Toland ◽  
Andreas Noack ◽  
Kristian Anastasiou ◽  
Richard Middlemiss ◽  
...  
Keyword(s):  
Proof Mass ◽  
Extreme Environments ◽  
Earth Tide ◽  
High Sensitivity ◽  
Glass Layer ◽  
Signal Conditioning ◽  
Magma Flow ◽  
Mass Displacement ◽  
Relative Gravimeter

<p><strong>Novelty / Progress Claim(s)</strong></p><p>This paper reports a capacitive readout-based MEMS relative gravimeter which can detect sub-Hz microseismic and slowly varying gravitational Earth tide signals. The gravimeter has a noise floor of 6-7 uGal/rt(Hz) at 1Hz and a linear drift of <250 uGal/day, metrics which are on a par with the commercially available gravimeters, and are leading in the field of MEMS accelerometers. The gravimeter is packaged in a standard ceramic-carrier and interfaced to a low-power, advanced FPGA-based readout. This setup is housed within a bespoke thermal enclosure, making the platform ideal for multi-pixel array-based implementation in the field.</p><p><strong>Background/State-of-the-Art</strong></p><p>Gravimeters are used to measure the local acceleration due to gravity (g). One of the emerging applications of gravimetry is in volcanology where gravimeters can be used to understand magma plumbing, providing information on volcanic activity/unrest events. However, this requires multi-pixel ‘gravity-imaging’ around volcanoes, a feat which is not possible using the expensive, complex, and large form-factor commercially available gravimeters.</p><p>Recently, researchers have developed MEMS-scale accelerometers which have excellent sensitivities but not yet demonstrated good long-term stability, making them non-viable for long-term monitoring of slow gravity changes (such as produced by magma flow). In a previous work, the authors have demonstrated an optical shadow-sensor readout based MEMS gravimeter with a sensitivity of 40 uGal/rt(Hz). Building on the work, a portable version of the gravimeter was also reported previously. The devices in both the setups were limited by the displacement noise of the optical shadow-sensor and the packageability of the setup.</p><p>In this paper, we are reporting a novel gravimeter which uses a capacitive-readout for sensing the proof-mass displacement, is embedded in a MEMS IC package, and uses advanced FPGA-based electronics for signal conditioning. The improved displacement sensitivity of the capacitive readout allows designing stiffer suspension-springs making the device more robust for operations in extreme environments. The acceleration sensitivity achieved using the new gravimeter is around 6-7 uGal/rt(Hz) at 1Hz, which is a significant improvement over the previous versions of the gravimeter. The device is currently being readied for field trials in the sectors of volcano gravimetry and oil & gas, showing the maturity of the technology.</p><p><strong>Methodology</strong></p><p>The reported gravimeter has a microfabricated silicon proof-mass which is suspended from thin flexures. Metal-combs are patterned on top of the proof-mass and a fixed glass layer with complementary combs is assembled to be at a close separation from the proof-mass. The overlapping combs act as a capacitor, the magnitude of which is dependent on the proof-mass displacement. The multi-layered gravimeter is embedded within a standard 32-pin ceramic DIP chip-carrier and wire bonded. The MEMS package is interfaced with analog signal conditioning electronics and a digital lock-in implementation is employed for converting the capacitance change into useful units (uGals).The electronics noise of the setup is measured to be <1 uGal. To reduce temperature-related effects, a mK active temperature control is implemented around the device. The packaged device is housed within a prototype thermal enclosure making the platform field-portable.</p>

scholarly journals Torsion-balance tests of the weak equivalence principle

2012 ◽  
Vol 29 (18) ◽  
pp. 184002 ◽  
Author(s):  
T A Wagner ◽  
S Schlamminger ◽  
J H Gundlach ◽  
E G Adelberger
Keyword(s):  
Equivalence Principle ◽  
Torsion Balance ◽  
Weak Equivalence ◽  
Weak Equivalence Principle ◽  
Balance Tests

A low-temperature high-sensitivity torsion balance magnetometer with in situ stator adjustment

2004 ◽  
Vol 75 (8) ◽  
pp. 2672-2677 ◽  
Author(s):  
A. J. Matthews ◽  
A. Usher ◽  
C. D. H. Williams
Keyword(s):  
Low Temperature ◽  
High Sensitivity ◽  
Torsion Balance

Thermal Drift of Convection-Based Micromachined Accelerometer

2007 ◽  
Author(s):  
Andy Bo Wu ◽  
John Jones
Keyword(s):  
Proof Mass ◽  
Low Cost ◽  
High Sensitivity ◽  
Working Fluid ◽  
Thermal Drift ◽  
Working Fluids ◽  
Temperature Changes ◽  
Heated Fluid ◽  
Sensitivity Changes ◽  
Convective Accelerometer

A novel micromachined accelerometer without proof mass, based on the buoyancy of a heated fluid around a polysilicon heater, has previously been developed and reported. Significant features of this class of accelerometer include low cost and the combination of high sensitivity with high survivability. However, one of its big disadvantages is thermal drift: the sensitivity changes rapidly as the ambient temperature changes. A recent numerical and experimental study has shown that the sensitivity of the convective accelerometer is a function of the Rayleigh number of the working fluid. Using this criterion, a few liquids were selected as potential working fluids to improve the sensitivity of the accelerometer. The CFD program ‘FLOTRAN’ was used to model accelerometer performance using each of these fluids. Based on FLOTRAN modeling, some fluids were selected for experimental investigation. The thermal drift of the accelerometer using different working fluids was documented and the reasons for this thermal drift were discovered. Based on this observation, some possible solutions were proposed to reduce or eliminate the thermal drift.

A DEDICATED TORSION BALANCE TO DETECT NEUTRINOS BY COHERENT SCATTERING ON HIGH DEBYE TEMPERATURE MONOCRYSTALS

2008 ◽  
Vol 23 (11) ◽  
pp. 1719-1728 ◽  
Author(s):  
I. CRUCERU ◽  
G. NICOLESCU ◽  
O. G. DULIU
Keyword(s):  
Debye Temperature ◽  
High Sensitivity ◽  
Coherent Scattering ◽  
Torsion Balance ◽  
Molybdenum Wire ◽  
Under Construction ◽  
Positive Results ◽  
Small Rotation

The possibility of detecting neutrinos by coherent scattering on high Debye temperature monocrystals such as sapphire is presented and discussed. Preliminary estimations showed that 1 MeV neutrinos with a fluency density of 1012 cm-2 s-1 could interact with a force of about 10-6 dyn with a 100 g sapphire monocrystal. A torsion balance provided with 1 m length molybdenum wire and an optical autocollimator able to measure small rotation angles of about 0.1 arcsec could give positive results. The design of a high sensitivity torsion balance under construction provided with such a detector is presented and discussed.

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