Bolt looseness testing system for basin insulators based on TMR sensor

Bolt connection structure is the main fixing method of insulator in high voltage overhead tower. Once bolt loosens, insulator will fall off due to uneven force.A bolt loosening detection method based on tunneling magnetoresistance (TMR) sensor was proposed. This method used the high sensitivity and high resolution of the TMR sensor to the magnetic field information to fix the sensor in the vertical direction of the bolt to be measured, and drived the target magnet according to the bolt loosening which resulting in the change of the magnetic field information, and finally achieved bolt loosening detection. The results showed that this method could realize the detection of bolt loosening angle of 0°~360°, and the resolution of the system was 0.1°, and the sensitivity was 0.5°/$\sqrt{Hz}$, and the error of detecting bolt loosening was no more than 1.8°, which provided a new method for bolt industrial detection.