Abstract: Novel proximity eddy current sensor array and its testing system are developed to realize the real-time inspection of the small gaps between large curved surfaces. The flexible sensor probe, manufactured by the flexible printed circuit board (FPCB) process, is designed to consist of a forked coils array with a long flat cable by the investigations to the design, process and substrate materials for the eddy current array. The time division multiplexing (TDM) technology is introduced for the eddy current array to scan and sample all the sensor coils. Some reforms are implemented to the conventional oscillator to solve the problem of the coils having a low Q-factor and improve the performance of the sensor system. Experimental results show that the measurement accuracy of the sensor system can reach ±0.5% for a 2 mm full scale and the sensor system is suitable for online gap measurements.

Key words: Coils array, Eddy current sensor, Flexible substrate, Proximity sensing, Time division multiplexing