Application of Lock-in Amplifier Technique in AC FSM based on AD630

Field Signature Method (FSM) is one of non-intrusive technique for pipeline internal corrosion monitoring, but the commercial FSM systems nowadays are all using DC input which have many shortcomings. In this paper, AC FSM based on AC input has been developed, DC FSM can be replaced by AC FSM with low-frequency. To extract weak signals, the lock-in amplifier based on AD630 has been designed and manufactured, the functions and designed circuits of each part have been proposed. Experimental results show that, the application of lock-in amplifier technique in AC FSM based on AD630 can measure the weak signal from the noise interference effectively, ensuring the accuracy and security at the same time. (paper)