Comparison of Sensor's Drift of Pressure Transducers by Sensing Mechanism

Pressure transducers have been commonly used as bottom pressure recorders (BPRs) for real-time tsunami monitoring in the ocean observatories. BPRs are potentially used for crustal deformation process before mega-thrust earthquakes, because they can detect change of ocean depth with higher resolution less than 1 mm. Observations of sensor's drift of BPRs have been reported after deploying in the deep-sea. Therefore, long-term stability is required in addition to the accuracy so that BPRs can detect crustal deformation. In this study, we evaluate sensors' drift of pressure transducers by applying constant pressure of 20 MPa (equivalent to 2,000 meters water depth) in the low temperature oil chamber (approximately 2 °C) in the laboratory. In the laboratory experiment, three kinds of pressure transducers in terms of pressure sensing mechanisms, i.e., the Bourdon tube quartz oscillator, thickness shear mode resonator (TSMR), and silicon resonant transducers are examined. As a result, pressure deviations of all pressure transducers are obtained after one month continuous pressure loading. Drift curves can be divided into two sections; initial response and the following sensor's drift. The drift of the Bourdon tube quartz oscillator transducers vary regarding the drift rate and the direction. All pressure transducers show drift less than 10 cm except for the initial response. It should be worth noting that thermal effect is little on the silicon resonant pressure sensor. The present study recommends that this kind of pre-evaluation regarding long-term stability may be needed so that pressure transducers would detect crustal deformation.