Analysis and Calculation of the Effective Length of a Reader Solenoid Coil Coupled to Rapidly Moving Microtag

This study investigated the effective length of the reader solenoid coil used for oil-well drilling, and the time required for the communication between rapidly moving microtags and the reader solenoid coil attached to the equipment pipeline was calculated. The effective length of the solenoid coil was computed for both static and moving microtags. Then, a mathematical model was developed to describe the relationship among the effective length of the reader solenoid coil, baud rate, number of data bits, and microtag speed. Calculations were performed to design two reader solenoid coils, which were tested experimentally with a carrier frequency of 125 ± 10 kHz. The results show that the effective length of the reader solenoid coil is proportional to the microtag speed and number of data bits but inversely proportional to the baud rate. The proposed system provides a continuous energy supply to the microtags, and the moving microtag identification rate by the reader is 100%. The experimental and calculation results were in good agreement. Furthermore, reader solenoid coils of two lengths were used in the downholes of six oil-well drilling systems over two years.