Broadband Frequency Response Assessment of Differential Pressure Gauge for Ocean Bottom Seismology Study

2019 ◽  
Author(s):  
Chau-Chang Wang ◽  
Huang-Chi Chang ◽  
Yih Yang
Keyword(s):  
Frequency Response ◽  
Pressure Gauge ◽  
Response Assessment ◽  
Differential Pressure ◽  
Ocean Bottom ◽  
Ocean Bottom Seismology ◽  
Broadband Frequency

In-Situ Calibration of Differential Pressure Gauges on OBSIP Ocean Bottom Seismometers

2020 ◽  
Author(s):  
Gabi Laske ◽  
Adrian Doran
Keyword(s):  
Pressure Sensor ◽  
Broad Band ◽  
Pressure Gauge ◽  
Differential Pressure ◽  
P Wave ◽  
Earth Tides ◽  
Release Mechanism ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer

<p>A standard ocean bottom seismometer (OBS) package of the U.S. OBS Instrument Pool (OBSIP) carries a seismometer and a pressure sensor. For broadband applications, the seismometer typically is a wide-band or broad-band three-components seismometer, and the pressure sensor is a differential pressure gauge (DPG). The purpose of the pressure sensor is manifold and includes the capture of pressure signals not picked up by a ground motion sensor (e.g. the passage of tsunami), but also for purposes of correcting the seismograms for unwanted signals generated in the water column (e.g. p-wave reverberations).<br>Unfortunately, the instrument response of the widely used Cox-Webb DPG remains somewhat poorly known, and can vary by individual sensor, and even by deployment of the same sensor.</p><p>Efforts have been under way to construct and test DPG responses in the laboratory. But the sensitivity and long‐period response are difficult to calibrate as they  vary with temperature and pressure, and perhaps by hardware of the same mechanical specifications.  Here, we present a way to test the response for each individual sensor and deployment in situ in the ocean. This test requires a relatively minimal and inexpensive modification to the OBS instrument frame and a release mechanism that allows a drop of the DPG by 3 inches after the OBS package settled and the DPG equilibrated on the seafloor. The seismic signal generated by this drop is then analyzed in the laboratory upon retrieval of the data. </p><p>The results compare favorably with calibrations estimated independently through post‐deployment data analyses of other signals such as Earth tides and the signals from large teleseismic earthquakes. Our study demonstrates that observed response functions can deviate from the nominal response by a factor of two or greater with regards to both the sensitivity and the time constant. Given the fact that sensor calibrations of DPGs in the lab require very specific and stable environments and are time consuming, the use of in-situ DPG calibration frames pose a reliable and inexpensive alternative. </p>

Piezoelectric Unimorph and Bimorph Cantilever Configurations: Design Guidelines and Strain Assessment

2022 ◽  
Author(s):  
Abhijeet Giri ◽  
Shaikh Faruque Ali ◽  
Arunachalakasi Arockiarajan
Keyword(s):  
Frequency Response ◽  
Piezoelectric Layer ◽  
Bending Moment ◽  
Adhesive Layer ◽  
Response Assessment ◽  
Design Guidelines ◽  
Induced Voltage ◽  
Design Variables ◽  
Piezoelectric Unimorph ◽  
Broadband Frequency

Abstract Multi-stable configurations of piezoelectric harvesters are quite successful in achieving the two important goals, the broadband frequency response and large orbit oscillations exhibiting periodic, multi-periodic, and chaotic solutions. However, in the quest of achieving large amplitude broadband frequency response, assessment of induced strain levels considering the limits on the strain in piezoelectric material has received minimal attention. In this context, the investigation presents an analytical formulation for the assessment of induced strain and voltage(s) in piezoelectric unimorph and bimorph cantilevers. The formulation quantifies not only the induced voltage(s) in individual piezoelectric layers of a bimorph, but also the equivalent voltages in parallel and series connection modes, respectively. Also, while computing the induced voltage in the first piezoelectric layer, the contribution from the induced voltage of the second piezoelectric layer to the acting bending moment is captured in the formulation. The formulations are validated through the experiments and results from the literature. Further, we have applied two practically useful normalization schemes, the tp- and tt-normalizations to the analytical expressions. Using the two normalization schemes, influences of variation of substrate and adhesive layer thicknesses, elastic moduli of layers, and substrate-to-composite length fraction are visualized and discussed. Based on the results, summarized guidelines for design and selection of geometric and material parameters are presented, which are also applicable for other sensing and actuation applications. At last, practically suitable ranges and optimum values for the normalized design variables are proposed.

scholarly journals Tracking deep-sea internal wave propagation with a differential pressure gauge array

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chu-Fang Yang ◽  
Wu-Cheng Chi ◽  
Hans van Haren ◽  
Ching-Ren Lin ◽  
Ban-Yuan Kuo
Keyword(s):  
Wave Propagation ◽  
Internal Wave ◽  
Pressure Gauge ◽  
Thermal Relaxation ◽  
Deep Ocean ◽  
Differential Pressure ◽  
Propagation Time ◽  
Ocean Bottom ◽  
Internal Motions ◽  
The Impact

AbstractTemperature is used to trace ocean density variations, and reveals internal waves and turbulent motions in the deep ocean, called ‘internal motions.’ Ambient temperature detected by geophysical differential pressure gauges (DPGs) may provide year-long, complementary observations. Here, we use data from four DPGs fixed on the ocean bottom and a high-resolution temperature sensor (T-sensor) 13 m above the seafloor as a square-kilometer array deployed offshore ~ 50 km east of Taiwan facing the open Pacific Ocean to examine the impact of temperature on DPG signals related to internal motions. The DPG signals correlate with T-sensor temperature variations between 0.002 and 0.1 mHz, but have time shifts partially caused by slow thermal conduction from the ambient seafloor to the DPG chamber and partially by internal motion propagation time across the array. Applying beamforming-frequency-wavenumber analysis and linear regression to the arrayed T-sensor and DPG data, we estimate the propagating slowness of the internal motions to be between 0.5 and 7.4 s m−1 from the northwest and northeast quadrants of the array. The thermal relaxation time of the DPGs is within 103–104 s. This work shows that a systematic scan of DPG data at frequencies < 0.1 mHz may help shed light on patterns of internal wave propagation in the deep ocean, especially in multi-scale arrays.

scholarly journals Frequency Response Characteristic (FRC) Curve and Fast Frequency Response Assessment in High Renewable Power Systems

2020 ◽  
Author(s):  
Shutang You
Keyword(s):  
Power Systems ◽  
Frequency Response ◽  
Real Time ◽  
Response Assessment ◽  
Response Characteristic ◽  
Assessment Method ◽  
Frequency Response Characteristic ◽  
Dynamic Simulations ◽  
Renewable Power ◽  
Response Performance

This letter introduces a frequency response characteristic (FRC) curve and its application in high renewable power systems. In addition, the letter presents a method for fast frequency response assessment and frequency nadir prediction without performing dynamic simulations using detailed models. The proposed FRC curve and fast frequency response assessment method are useful for operators to understand frequency response performance of high renewable systems in real time.

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