5:15 PM - 7:15 PM
[SCG55-P32] Quantitative evaluation of accuracy and precision for the RBR pressure sensor based on the laboratory experiment
Keywords:Seafloor Pressure Monitoring, Sensor Accuracy Evaluation, Pressure-Resistant Container Development
At the Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, seafloor water pressure observations have been continuously conducted since 2008 with the aim of monitoring seafloor vertical crustal deformation along the Japan Trench and the Kuril Trench, primarily off the coast of Miyagi Prefecture.
In these observations, a high-precision Paroscientific Digiquartz Series8B (hereinafter referred to as the "Paroscientific sensor") is employed. This sensor is housed in a titanium pressure-resistant container and, with an in-air weight of 3.4 kg and a water weight of 2.8 kg, is capable of high-precision water pressure measurements in environments up to 7000 m deep (70 MPa). It has been used in numerous field deployments. However, the relatively high power consumption of the entire system, including the data logger, hinders long-term seafloor observations, and the high procurement cost of the sensor itself also presents a challenge.
Meanwhile, in recent years, low-cost water pressure sensors designed for geoscience applications have emerged. One such sensor is the RBR Duet3T.D. (hereinafter referred to as the "RBR sensor"). This sensor is small and lightweight 0.4 kg in air and 0.07 kg in water-and achieves low power consumption by integrating the sensor and its data logger. Although it is less expensive than the Paroscientific sensor, evaluations of its accuracy and precision remain insufficient. Therefore, an indoor pressurization experiment was conducted to assess the accuracy of the RBR sensor.
Because the pressure-sensing part component of the RBR sensor is directly attached to its body, it is impossible to perform tests by directly connecting pressure piping. Consequently, it became necessary to fabricate a pressure-resistant container to enclose the entire sensor for the pressurization experiment. To that end, in August 2021 a prototype was manufactured with the cooperation of the Instrument Development and Training Laboratory, Graduate School of Science, Tohoku University. Furthermore, to ensure a stable test environment, an improved version (Ver.2) was produced in November 2023, and Ver.3 aimed at further enhancing pressure performance was completed in June 2024.
In Ver.3, the pressure transmission medium was changed from pure water to dioctyl sebacate, and, to improve pressurization efficiency, the void fraction within the container volume was reduced from 33.6% (Ver.2) to 22.6%. This pressurization experiment, using the pressure-resistant container, was carried out with the pressure standard at the National Institute of Advanced Industrial Science and Technology (AIST) in a thermostatic water bath to maintain a constant temperature, thereby allowing for a quantitative evaluation of the pressure measurement accuracy of the RBR sensor. This report describes the results.
In these observations, a high-precision Paroscientific Digiquartz Series8B (hereinafter referred to as the "Paroscientific sensor") is employed. This sensor is housed in a titanium pressure-resistant container and, with an in-air weight of 3.4 kg and a water weight of 2.8 kg, is capable of high-precision water pressure measurements in environments up to 7000 m deep (70 MPa). It has been used in numerous field deployments. However, the relatively high power consumption of the entire system, including the data logger, hinders long-term seafloor observations, and the high procurement cost of the sensor itself also presents a challenge.
Meanwhile, in recent years, low-cost water pressure sensors designed for geoscience applications have emerged. One such sensor is the RBR Duet3T.D. (hereinafter referred to as the "RBR sensor"). This sensor is small and lightweight 0.4 kg in air and 0.07 kg in water-and achieves low power consumption by integrating the sensor and its data logger. Although it is less expensive than the Paroscientific sensor, evaluations of its accuracy and precision remain insufficient. Therefore, an indoor pressurization experiment was conducted to assess the accuracy of the RBR sensor.
Because the pressure-sensing part component of the RBR sensor is directly attached to its body, it is impossible to perform tests by directly connecting pressure piping. Consequently, it became necessary to fabricate a pressure-resistant container to enclose the entire sensor for the pressurization experiment. To that end, in August 2021 a prototype was manufactured with the cooperation of the Instrument Development and Training Laboratory, Graduate School of Science, Tohoku University. Furthermore, to ensure a stable test environment, an improved version (Ver.2) was produced in November 2023, and Ver.3 aimed at further enhancing pressure performance was completed in June 2024.
In Ver.3, the pressure transmission medium was changed from pure water to dioctyl sebacate, and, to improve pressurization efficiency, the void fraction within the container volume was reduced from 33.6% (Ver.2) to 22.6%. This pressurization experiment, using the pressure-resistant container, was carried out with the pressure standard at the National Institute of Advanced Industrial Science and Technology (AIST) in a thermostatic water bath to maintain a constant temperature, thereby allowing for a quantitative evaluation of the pressure measurement accuracy of the RBR sensor. This report describes the results.