Resonance Frequency Detection Research Articles

On-Line Wear Debris Detection in Lubricating Oil for Condition Based Health Monitoring of Rotary Machinery

Condition based monitoring has become essential in maintaining and extending the health of high-speed rotating and reciprocating machinery. One effective approach to detect signs of potential failure of a rotating or reciprocating machine is to examine the wear debris in its lubricating oil. Recent patents and research articles on on-line wear debris detection in lubricating oil are reviewed in this paper, including electrical impedance detection, acoustic detection, optical detection, pressure detection, online x-ray spectrography, resonant frequency detection, and electrostatic charge detection. Advantages and limitations of each detection method are discussed. Keywords: Debris, condition monitoring, on-line detection, particle sensor, condition-based maintenance

Suspended microchannel resonators with piezoresistive sensors

Precision frequency detection has enabled the suspended microchannel resonator (SMR) to weigh single living cells, single nanoparticles, and adsorbed protein layers in fluid. To date, the SMR resonance frequency has been determined optically, which requires the use of an external laser and photodiode and cannot be easily arrayed for multiplexed measurements. Here we demonstrate the first electronic detection of SMR resonance frequency by fabricating piezoresistive sensors using ion implantation into single crystal silicon resonators. To validate the piezoresistive SMR, buoyant mass histograms of budding yeast cells and a mixture of 1.6, 2.0, 2.5, and 3.0 µm diameter polystyrene beads are measured. For SMRs designed to weigh micron-sized particles and cells, the mass resolution achieved with piezoresistive detection (∼3.4 fg in a 1 kHz bandwidth) is comparable to what can be achieved by the conventional optical-lever detector. Eliminating the need for expensive and delicate optical components will enable new uses for the SMR in both multiplexed and field deployable applications.

Interrogation strategies for probing wireless passive SAW sensors

Surface acoustic wave devices are now widely used for monitoring physical quantities such as temperature or stress. The intrinsic radio-frequency (RF) nature of these devices makes them ideal for wireless and passive sensor applications. We develop an interrogation unit following the principles of a frequency sweep network analyzer. The wireless interrogation of the resonance frequency of acoustic resonators induces the additional necessity of switching on and off the radiofrequency RF emission in a manner similar to that used in RADARs to comply with the regulations in the 433.4MHz, 1.7MHz wide, European ISM band. We assess the interrogation range, as well as the accuracy of the measurement and we develop various software strategies enabled by the fully digital nature of the radiofrequency RF synthesis chain. We particularly demonstrate the advantage of using different strategies depending on measurement application. The first strategy we have selected for interrogating narrow-band devices is a slow sweep of a frequency source with a spectral response narrower than that of the passive acoustic resonators. The basic principle is similar to that used by network analyzers, although the wireless link induces an additional constraint, namely the alternation of emission and reception phases as used in RADAR strategies with unique improvements such as emitting a probe pulse with a spectral width narrower than the resonance width at half height. We have presented previously [1] the digital processing steps used to improve the resonance frequency identification resolution, using a second-order polynomial fit. However, although a frequency-sweep network analyzer approach reduces the requirements in terms of sampling rate and memory capacity, the global interrogation duration is increased due to the many frequency steps required for accurately identifying the resonance frequency. Considering that each interrogation step requires 60μs and 128 steps necessary to find two resonant frequencies, 7.7ms is necessary to get a measurement. An alternative approach uses a feedback control to track the resonance frequency. Therefore, 3 interrogation points are enough to locate the resonant frequency, providing a measurement in 360μs. Once initialized, this three probe pulses strategy allows for detecting the resonance frequency with sub-100Hz resolution in the 434MHz ISM band. The second strategy uses a frequency-modulation-based interrogation strategy [2]. The conversion of frequency modulation to amplitude modulation by radiofrequency resonators hence reveals an accurate way to determine the resonance frequency of wireless passive sensors. Along this strategy, an interrogation strategy has been developed exploiting the cancellation of an amplitude modulated signal resulting from the conversion of the FM-to-AM conversion via the transfer function of the resonator. A feedback loop control based on this approach yields a resonance frequency detection with sub-25Hz resolution in the 434MHz ISM band with an acquisition rate around 1Hz. The third strategy is using a Universal Software-Radio Peripheral (USRP) running the GNURadio software to detect resonance frequencies by Fourier transform [3]. We compare the three strategies concerning accuracy, refreshing delay, detection distances and cost issues.

Predicting the Enantioseparation Efficiency of Chiral Mandelic Acid in Diastereomeric Crystallization Using a Quartz Crystal Microbalance

This study uses quartz crystal microbalance (QCM) chiral recognition as a novel approach to predict the chiral recognizability of a chiral selector for a racemate. The chiral selector (l-phenylalanine, l-Phe) was immobilized on a QCM sensor surface using a two-step assembly procedure. The modification of the l-Phe on the sensor surface was then characterized using several techniques, including resonant frequency detection, the contact angle, and X-ray photoelectron spectroscopy measurements. When examining the chiral recognizability of the l-Phe-modified QCM sensor for l-mandelic acid (l-MA) using a vapor diffused molecular assembly reaction technique, the chiral discrimination factor between l- and d-MA was about 8. The practical diastereomeric crystallization resolution of a MA racemic compound was then carried out using l-Phe as the resolving agent. The different properties of the diastereomer crystals of l-Phe-l-MA and l-Phe-d-MA were confirmed using high performance liquid chromatography (HPLC) and differential scanning calorimetry (DSC) analysis, plus the factors influencing the chiral resolution, such as molar ratio of MA to l-Phe, agitation speed, pH, cooling rate, and crystallization temperature were examined. The results showed that the diastereomeric crystallization separation of racemate MA using l-Phe as the resolving agent matched well with the QCM chiral recognition results. Therefore, the proposed method using QCM chiral recognition offers a simple solution to the challenge of screening a resolving agent for diastereomeric crystallization.

Note: Exciting higher-order flexural modes of freestanding microstructures with square wave driving signals

We examine using the harmonics of low fundamental frequency (f(1)) square waveforms to electrostatically excite higher-order flexural modes of a micromechanical structure in higher (>f(1)) frequency regimes. Square wave signals swept between a fundamental frequency range of approximately 0-333 kHz demonstrated an effective high magnitude spectral excitation of approximately 0-1 MHz. This enabled optical heterodyne detection of structural resonant frequencies above 333 kHz. Low frequency square wave signals were also used to selectively excite modes at higher frequencies.

Silicon-based micromembranes with piezoelectric actuation and piezoresistive detection for sensing purposes in liquid media

In this paper, the authors report for the first time the physical cointegration of piezoelectric actuation and piezoresistive detection on resonating micromembranes dedicated to microgravimetric biosensing applications. The micromembranes are oscillated by a reverse piezoelectric phenomenon provided by a PbZrxTi1−xO3 46/54 thin layer. The oscillation amplitudes are read-out by measuring the resistance change of piezoresistors precisely located on the clamped edges of each micromembrane. The detection of the micromembranes' resonant frequencies is reported in air and deionized water. A dedicated electronic set-up operating the micromembranes in a closed-loop configuration is described. The set-up enables multiplexed tracking of four micromembranes' resonant frequencies in liquid media while enhancing the corresponding quality factors' values. Increases up to 11-fold of the micromembranes' quality factors in liquid is reported for the (0,1) vibration mode. A quality factor of up to 417 is reported in fluid.

Fully integrated FBAR sensor matrix for mass detection

A fully integrated Film Bulk Acoustic Resonator (FBAR) based mass detection sensor matrix was developed for label-free in-vitro DNA and protein diagnostics. A 64 pixels sensor matrix was post-processed on top of a CMOS readout circuitry at wafer level. A novel and patented resonance frequency detection method was developed. To our knowledge this is the first realized full integrated FBAR matrix sensor.

Quantitative force and mass measurements using the cantilever with integrated actuator and deflection detector

Applications based on cantilever sensor technology like atomic force microscopy, mass spectroscopy, magnetic resonance force microscopy, and other physical or chemical sensing techniques demand theoretical understanding of sensing and actuation mechanism. Moreover reliable calibration of any instrumentation is necessary in order to enable comparison of obtained results between various laboratories. When mass or force investigations are performed in nanoscale the reliable system calibration is even more difficult due to the lack of appropriate references and established metrological techniques. In this article we present the calibration methodology of thermally driven piezoresistive cantilevers which were used for mass and force measurements. We adapt the mass loading spring constant calibration method and compare the results obtained in this way with the method which was based on the resonance frequency detection. Additionally we will present results of the cantilever deflection sensitivity measurement and low-frequency noise properties.

A focused-ion-beam-fabricated micro-paddle resonator for mass detection

An experimental microelectromechanical system paddle resonator was made using focused ion beam fabrication from a 200 nm thick silicon nitride membrane and investigated using a laser vibrometer for resonant frequency detection. The fundamental mode was found to be torsional, as required, with a resonant frequency of 1.38 MHz and Q of 1070 at a test pressure of 20 μbar. The mass sensitivity was 55 ag Hz−1, close to the results of analytical and finite element analysis modeling, demonstrating proof of principle.

High quality factor gigahertz frequencies in nanomechanical diamond resonators

We report actuation and detection of gigahertz-range resonance frequencies in nanocrystalline diamond mechanical resonators. High order transverse vibration modes are measured in coupled-beam resonators exhibiting frequencies up to 1.441GHz. The cantilever-array design of the resonators translates the gigahertz-range resonant motion of micron-long cantilever elements to the displacement of the central supporting structure. Use of nanocrystalline diamond further increases the frequency compared to single crystal silicon by a factor of 3. High clamping losses usually associated with micron-sized straight beams are suppressed in the periodic geometry of our resonators, allowing for high quality factors exceeding 20 000 above 500MHz.

Passive Telemetric Readout System

A technique for remote query monitoring of environmental parameters such as pressure, humidity, complex permittivity, temperature, strain, and gases such as carbon dioxide, oxygen, and ammonia is presented. Resonant peak passive telemetry is used for wireless remote monitoring. The resonance frequency of an inductor-capacitor sensor circuit changes with the surrounding environmental parameter, and a detector circuitry, which employs a loop antenna, is used to remotely identify the resonance frequency. Mutual coupling between the antenna and the sensor inductor enables wireless monitoring. Various detection techniques available for monitoring the sensor resonance frequency are examined, and a new method is presented for automated and continuous wireless detection of sensor resonance frequency. Results are presented for different sensor resonance frequencies using various sensor capacitance values. The designed system can effectively detect sensor resonance frequency variation in the range of 20 kHz-10 MHz with the highest achievable resolution of 0.01 MHz. Sensor resonance frequency changes that occur faster than 1 s cannot be detected. The automated continuous wireless remote sensor platform design provides significant advantage over past systems, and the entire design is simple, easy to use, and widely applicable for in vivo, in vitro, and in situ monitoring

Cantilever based mass sensor with hard contact readout

We present a method for microcantilever resonant frequency detection. We measure the direct current from an intermittent contact once every vibration cycle between the conducting cantilever and a counterelectrode at a low bias voltage with respect to the cantilever, while the excitation frequency and amplitude are varied. The result is an almost “digital” detection of the resonant frequency. A relative frequency resolution Δf∕f of 1∕80000 with high signal to noise ratio in ambient conditions is demonstrated. The detection method can be applied to portable sensor systems with very high frequency nanoelectromechanical cantilevers using simple off-chip electronics.

Theory of direct frequency output vibrating gyroscopes

Vibrating gyroscopes are instruments for measuring the angular velocity of a system with respect to an inertial reference frame. Most currently available vibrating gyroscopes are based on the excitation of a reference vibration in the plane of a vibrating structure, and the amplitude detection of the vibration normal to the plane induced by the Coriolis effect, which is proportional to the angular velocity of the applied rotation. This paper describes a new vibrating gyroscope based on the simultaneous driving of the two modes of vibration (in plane and out of plane) and the detection of resonance frequencies. It is shown, in this paper, that the resonance frequencies of the two modes vary with the applied angular velocity, and that the difference between them is approximately proportional to the applied angular velocity. It is demonstrated that this kind of gyroscopes presents a lock-in effect related to the natural frequencies and the driving electronics. The results obtained are fundamental to the design of this kind of gyroscopes.

Inverse determination of porosity from object’s resonances

An alternative technique combining vibroacoustography and the finite element method for measuring the porosity parameter P and damping of a chalk sphere immersed in water is presented. This technique is based on the detection of the sphere resonance frequencies which will be compared to the finite element calculations. An optimization procedure based on the least squares method is performed in order to evaluate the “effective” Young’s modulus and damping parameters. Hence, porosity can be estimated by an inverse expression from the effective Young’s modulus.

An automated method for the detection of field line resonance frequencies using ground magnetometer techniques

This report describes an automated method developed to quickly and precisely determine field line eigenfrequencies from ground magnetometer data using the statistical properties of cross‐phase and power ratio spectra. This new automated method allows for routine monitoring of field line resonant frequencies, and hence plasma mass density of the inner magnetosphere, with better temporal coverage and over longer intervals than previous studies, which were limited simply due to the time‐consuming nature of making selections “by hand.” To demonstrate the usefulness of the automated procedure, 2 years of data from a pair of magnetometers in the MEASURE array at L = 1.74 were analyzed, and the annual variation in plasmaspheric density was observed. The equatorial mass density reaches a maximum in the Northern Hemisphere winter, and a minimum in summer, with winter values two to three times higher than in summer. This result confirms previous whistler observational studies and theoretical modeling studies.

High-resolution detection of resonant frequencies of microwave resonators via magnetic measurements

An experiment with high spin molecular magnets inside microwave resonators has produced the remarkable observation of sharp peaks in the equilibrium magnetization and the ac susceptibility for the resonant frequencies of these devices. These peaks appear when the magnets are pumped or warmed by microwaves to states of different magnetic moment, and allow one to carry out spectroscopic studies of either the magnetic materials or the resonant device.

Nanocantilever signal transduction by electron transfer.

Microfabricated cantilever beams promise to bring about a revolution in the field of chemical, physical, and biological sensor development. The resonance frequency of a microfabricated cantilever shifts sensitively because of mass loading from molecular adsorption. The minimum detectable adsorbed mass on a cantilever sensor can be increased by orders of magnitude by changing the dimensions of the device; smaller and thicker cantilevers offer higher resonance frequency and therefore better mass detection sensitivity. Here we describe micromachined silicon cantilevers that are 0.5 to 4 microns in length, fabricated with the use of a focused ion beam (FIB). In addition, we demonstrate a technique for detection of the cantilever resonance frequency that is based on electron transfer.

Determination of liquid density with a low frequency mechanical sensor based on quartz tuning fork

A novel sensor is presented for measuring liquid density. It consists of a PZT rectangular plate as an actuator for piezoelectric excitation and a quartz tuning fork placed on top of PZT as a sensor for resonant frequency detection. The resonant frequency is determined from the sensing voltage created in tuning fork when the excitation frequencies of PZT actuator are swept around the resonant frequencies of tuning fork. And the liquid density result is extracted from the resonant frequency. The density values of five kinds of organic solvents are measured and compared with the standard values. All experimental results are in agreement with the standard values and the maximum standard deviation is less than ±8%.

建設材料 インパクトエコー法によるＰＣグラウト充てん度評価に関する考察

Impact-echo technique is a method for nondestructive evaluation, detecting elastic waves due to a mechanical impact. Although the impact-echo is reported to be promising for quantitative estimation, an applicability to evaluation of post-tensioning tendon ducts is not confirmed yet. To this end, the basic theory of the impact-echo should be clarified. In this paper, a specimen containing an ungrouted duct is tested. Theoretically, frequency responses of the specimen depend on the size, orientation of the void, and P-wave velocity, while wave motions in concrete structures are characterized by material properties, incident waves, and size of members. Thus, the frequency response is studied from the relationship between the wave length and the depth of duct. Experimentally, impact tests are conducted by dropping steel balls and shooting aluminum bullets. The analysis is carried by the boundary element method (BEM). As a result, the detection of resonance frequency due to the presence of void is clarified, relating with impact frequencies and the depth of duct.

Accurate Resonance Frequency Detection in a Microwave Moisture Measurement

This paper describes a technique for accurate resonance frequency detection of a moisture measurement system using a dielectric ring resonator operating at a center frequency of about 2.1 GHz by eliminating the influence of noise superimposing on the resonant curve. The curve fitting midpoint method is the most effective one among the three methods examined in this study. The cardboard samples with about 5 to 115 % moisture on a dry basis were measured using the curve fitting midpoint method. The standard deviation of the predicted moisture contents is 1.14 % (d.b.) over the whole range of moisture contents measured.