Development of Probe for Resistivity Measurement in Borehole of Coal Mine

To better serve the coalfield geological fine exploration and the disaster prevention and mitigation work in the process of coal mining, a method for measuring the resistivity of the borehole section to identify the geological anomaly area using the immersive bore-in-hole resistivity measuring probe is proposed. Based on the symmetrical four-stage device measurement model, we design a signal generation unit capable of generating an adjustable sinusoidal excitation current with a frequency between 0 to 1 MHz, and design a signal acquisition unit with the function of automatic range conversion, including a fully differential amplifier circuit and a high speed AD circuit, and finally use the linear regression analysis method to calibrate the device coefficient K of the developed in-hole resistivity measuring probe. The performance test results show that the resistivity probe has a measurement error of 0.2%, which satisfies the demand of fine detection in hole of coal mine.