Pulsed Eddy Current Displacement Sensor Measurement Technology For Coiled Tube

As for shale gas exploration in recent years, the dosage of the coiled tubing has increased dramatically. In order to guarantee the safety in the process of using, it is particularly important to monitor and test online. Common defects forms of coiled tube have surface pitting, sulfide stress cracking, fatigue pitting, mechanical indentation and ovality changing which is easy to cause the major security incidents because of leakage.Starting from the ovality definition, it illustrates that the ovality measurement transforms for the measurement of diameter in nature. Measuring ovality can be measured through the distance between sensor and coiled tube indirectly. Starting from the measurement principle of pulsed eddy current displacement sensor, it establish coil response model and puts forward a method to eliminate the oscillation. Using self-made sensor test the typical absolute type and differential type pulse eddy current signal; Compare the different structure of the pulsed eddy current displacement sensor signal, select upright concentric differential structure of sensor as a displacement sensor; Contrast the signal of three kinds of sensors(namely coreless, adding 45 steel core, adding ferrite core), peak value of adding ferrite core assembling magnetic sensor change a lot. Through the test of static calibration of self-made pulsed eddy current displacement sensor, it indicates that displacement and peak variation is nonlinear monotone decreasing relationship, by introducing three kinds of sensor displacement fitting with voltage(polynomial fitting, exponential fitting and linear interpolation fitting), using the SSE(variance), R-square(decision coefficient), RMSE(standard deviation) three indicators analysis, it is concluded that the best way of fitting. By the static calibration of self-made pulsed eddy current displacement sensor displacement and peak variation is nonlinear monotone decreasing relationship, by polynomial fitting, exponential fitting and linear interpolation of three kinds of sensor displacement fitting with voltage value, using three indicators(SSE,R- square, RMSE) analysis, it is concluded the best way of fitting.According to the method of measuring, it designs array pulsed eddy current ranging signal system, including the hardware design and software design. The hardware system is divided into incentive part and receiving part. Incentive part includes the design of the pulse source, the voltage amplification circuit and Wattage amplifier circuit; Receiving part includes the design of the amplifier circuit, filter circuit, the display circuit. System software includes the program design of pulse signal, A/D conversion and data processing, LCD display.