In this paper, the design of strain measuring sensor technology of geophysical comprehensive observations in deep boreholes, the measurement principles of the capacitive displacement sensor are generally introduced. And the sensor adjustment technology is described in details. Signal conversion circuit, low-power data acquisition and remote data communication and control are illustrated.
In order to improve earthquake prediction, particularly in enhancing the ability to track temporary seismic section, the development environment suitable for the underground observation is chosen for more than one underground test items of the integrated observing system (Chen et al. 1995), mainly including the underground observation broadband seismometer, tilt-meter, component strain sensor (1983.), magnetometer and temperature measurement instrument (Su 2003). It is of great significance to the research of the underground sealing technology, the positioning technology and the system integration technology to develop the underground access to the integrated data acquisition and data transmission technology. Using the RS422 communications technology, we can achieve real-time observation data transfer or transfer by the command and realize the value of command-control cell-site calibration of sensors and other control functions. As the cylinder diameter of 10 cm, the resolution of displacement observation is needed to be better than 0.01 nm. The problem of resolution of strain measuring sensor can be solved by using the capacitive displacement sensor (Gladwin et al. 1984). Using the capacitance sensor with high stability source through the lock-in amplification and filter circuit, the amount of displacement to voltage conversion is completed. High stability of the calibration units is to achieve the sensor calibration; Use of motor-driven and fine machining of the dry cell is to achieve sensor zero adjustment; High-performance low-power processors and 24-bit ADC chip is used. The RS-422 is used for the digital transmission.
