47results about How to "Avoid the effects of electromagnetic interference" patented technology

Disclosed is a coal mine top plate aquiclude stability monitoring system based on a fiber Bragg grating. A measurement station is arranged on a work surface mining roadway, a vertical top plate drilling hole is drilled in a top plate of the work surface mining roadway to an aquiclude, a fiber Bragg grating pressure sensor is arranged at the top end of the drilling hole, a fiber Bragg grating top plate bed separation instrument is installed at the height position of the drilling hole between the aquiclude and a rock stratum below, and an optical fiber connector is led out of the drilling hole and connected with an optical fiber tail fiber, thereby being connected with an optical fiber splitter. The optical fiber connector is connected with an optical fiber terminal box through a communication optical fiber and connected to an optical fiber interrogator of a ground control chamber through a mining optical cable, signals are transmitted to a monitoring server after demodulation and are processed through the monitoring server, and the data processing result is shared with a client side through a mine local area network. The stability conditions of the aquiclude are monitored in real time through a computer display, and an alarm is given timely when the stress is near the bearing upper limit of the aquiclude and separation occurs between the aquiclude and the overlying strata blow.

The invention discloses a roadway surrounding rock stress monitoring device based on fiber bragg grating sensing. Grooves are symmetrically carved in a metal rod along the axial center, an FBG set is fixedly installed inside each groove, FBGs serve as sensitive elements, when roadway surrounding rock is deformed, the stress of the surrounding rock will be changed, therefore, force is generated through the metal rod, surface micro-deformation is generated, the grating distances of the FBGs attached to the metal rod are changed along with the metal rod, the center reflection wavelength of the FBGs can be caused to generate drifting, wavelength signals are demodulated into electrical signals through an FBG interrogator, and the stress situations of different sites can be obtained. The roadway surrounding rock stress monitoring device has the advantages that installation is easily achieved, and the roadway surrounding rock stress monitoring device is suitable for wide popularization; power is not required to be supplied to the working face end, and site safety is guaranteed; all-optical measurement and fiber transmission are adopted, and influences of electromagnetic interference are effectively avoided; the temperature error is compensated, and the accuracy is improved; the surrounding rock stress monitoring results can be timely and accurately provided, and guidance on site production and scientific research is facilitated.

The invention relates to a surrounding rock stress on-line monitoring system and method based on a fiber bragg grating borehole stress meter. A plurality of measurement points are arranged on a surrounding rock, the fiber bragg grating borehole stress meter is installed in a surrounding rock wall drill hole, an optical fiber connector is connected with an optical fiber, and the optical fiber is connected to a mining optical cable, is then directly connected to the ground, and is connected with a fiber bragg grating modulator; an optical signal is modulated to a digital signal by the fiber bragg grating modulator, the digital signal is transmitted to a computer, is monitored in real time and is analyzed and processed, and a surrounding rock axial stress and transverse stress analyzing and processing method is provided under the temperature compensation condition according to grating stress characteristics. The surrounding rock stress on-line monitoring system and method have the advantages that equipment is easy to install, long in service life and suitable for popularization and use; power supply is not needed underground, electrical signals and electronic devices do not exist, and therefore the field is safe; because all-optical measurement and optical fiber transmission are adopted, monitoring precision is greatly improved, and effect of electromagnetic interference can be effectively avoided under complex and poor environment; surrounding rock stress monitoring results can be provided in time and guiding of field production and scientific research work is facilitated.

The invention provides a preparation method of a humidity sensitive grating. The preparation method comprises the following steps: firstly, conducting hydrolysis and impurity removal on plant fibers to obtain a clean solution; conducting desugaring on the clean solution by a certain quantity of ketene or acetic anhydride; then under the action of acid, esterfying a hydroxyl functional group of cellulose to form an acetyl functional group; modifying the surface of the grating by a silane coupling agent so as to change hydroxyl on the surface of the grating into an amido group which is easy to bond with acetyl and comprises silane; cleaning and drying the grating of the amido group comprising silane, placing the grating into the solution of cellulose comprising acetyl to soak so as to form the humidity sensitive grating grafted with cellulose; finally, cleaning and drying the humidity sensitive grating and enabling the plant fibers on the surface of the grating to be connected mutually to form a coating layer. The invention further provides a fiber bragg grating temperature and humidity sensor prepared according to the preparation method of the humidity sensitive grating. The fiber bragg grating temperature and humidity sensor prepared according to the preparation method of the humidity sensitive grating can be simultaneously sensitive to temperature and humidity.

The invention discloses a filling body transverse deformation online monitoring system based on fiber bragg grating sensing, and relates to the technical field of mine filling body monitoring. The device comprises a bidirectional displacement measuring device based on fiber bragg grating sensing, a fixed disc, a coupler, an optical fiber, a mining optical cable, a fiber bragg grating demodulator and a computer system, the bidirectional displacement measuring device based on fiber bragg grating sensing comprises a measuring main body, an extension line, a steel pipe and two fiber bragg gratingdisplacement sensors, wherein the measuring main body comprises a shell and an upper cover matched with the shell; the shell is of a hollow cuboid structure, the left side and the right side of the shell are each provided with an outlet, the movable pull rods of the two fiber bragg grating displacement sensors penetrate through the outlets in the left side and the right side respectively and facethe outlets in the left side and the right side of the shell, and the axes of the movable pull rods are overlapped with the axes of the corresponding outlets. Real-time and on-line remote monitoring of the left side, the right side and the total transverse deformation of the filling body can be achieved.