Fiber Optic Thermo-Hygrometers for Soil Moisture Monitoring

326

236

There is an ever-growing demand for measuring respiratory variables during a variety of applications, including monitoring in clinical and occupational settings, and during sporting activities and exercise. Special attention is devoted to the monitoring of respiratory rate because it is a vital sign, which responds to a variety of stressors. There are different methods for measuring respiratory rate, which can be classed as contact-based or contactless. The present paper provides an overview of the currently available contact-based methods for measuring respiratory rate. For these methods, the sensing element (or part of the instrument containing it) is attached to the subject’s body. Methods based upon the recording of respiratory airflow, sounds, air temperature, air humidity, air components, chest wall movements, and modulation of the cardiac activity are presented. Working principles, metrological characteristics, and applications in the respiratory monitoring field are presented to explore potential development and applicability for each method.

Section: Figurementioning

confidence: 99%

Contact-Based Methods for Measuring Respiratory Rate

Massaroni

Nicolò

Presti

et al. 2019

326

236

“…The fiber optic sensing technology is characterized by strong anti-electromagnetic interference [6], strong corrosion resistance, high resolution and long-distance transmission [7]. It has been widely applied in many fields of the slope, such as the monitoring of surface deformation [8] and subsurface deformation [9] of the slope, the strain field [10,11] and the soil pressure [12] of the slope, the hydraulic characteristics [13,14] and the rockfall [15]. In the slope model test, fiber optic sensing technology has been used to monitor surface deformation [16] and subsurface strain [17] of the slope model, and multi-parameter monitoring for the geotechnical centrifuge model [18,19].…”

Section: Introductionmentioning

confidence: 99%

High Precision, Small Size and Flexible FBG Strain Sensor for Slope Model Monitoring

Zheng

Zhao

et al. 2019

In this paper, a soft fiber Bragg grating (FBG) strain sensor was constructed of a rubber strip, FBGs and steel plates, which exhibits the advantages of high precision and a small size. A series of FBGs was uniformly pasted on a flexible rubber strip which can monitor the slope deformation by measuring the bending deformation of the rubber strip. Most notably, this sensor can be used to monitor horizontal displacement in the subsurface of the slope model. The relationships among the bending angle of the rubber strip, the strain of the rubber strip, and the subsurface deformation of the slope model were established. In addition, the subsurface deformation of the slope model can be obtained by the FBG strain sensor monitoring. Since a rigid-flexible structure was formed by uniformly pasting a series of steel plates on the other side of the rubber strip, the sensitivity of the FBG strain sensor was improved to be 1.5425 nm/°. The measurement results verify that the FBG strain sensor shows good performance, and the model test results demonstrate that the FBG strain sensor can be used for monitoring the subsurface deformation of the slope model.

“…At the same time, fiber optical sensing technologies have also been widely used in landslide monitoring due to their small size, high resolution, and in-site monitoring and multiplexing capabilities [11,12,13,14]. Previous studies have established that surface deformation [15,16], subsurface deformation [17,18,19,20], reinforcements [21,22,23,24,25], the strain field [26,27,28,29], soil pressure [30,31], rockfall [32], and hydraulic characteristics [33,34,35] can be well-measured using fiber Bragg grating (FBG) sensors and Brillouin-based distributed sensors. Because of the complicated mechanisms and diverse triggering factors, information on multiple parameters is crucial in a practical application to evaluate the safety of a slope accurately [6,36].…”

Section: Introductionmentioning

confidence: 99%

A Highly Integrated BOTDA/XFG Sensor on a Single Fiber for Simultaneous Multi-Parameter Monitoring of Slopes

Zhao

et al. 2019

A highly integrated sensing technology, combining a stimulated Brillouin scattering-based distributed sensor with XFG (fiber Bragg grating (FBG) and long-period fiber grating (LPFG)) sensors on a single fiber, is proposed for the simultaneous measurement of fully distributed and multiple discrete dynamic strains/temperatures. A multiparameter monitoring scheme for slope safety is developed using this integrated sensing technology. An indoor simulation test is carried out to verify its ability to simultaneously monitor a slope’s surface displacement, an anchor reinforcement’s axial force, and rockfall vibration. The experimental results show that distributed static strain and discrete dynamic strain can be well-measured simultaneously with little interference. The results also demonstrate the XFG sensors’ capability for multi-type and multipoint multiplexing. In addition, the proposed hybrid sensor system has potential for the monitoring of multiple slope parameters simultaneously.