Design and Realization of External Monitoring System for Pipeline Internal Corrosion Based on AC FSM

T48 external monitoring for pipeline internal corrosion based on field signature method (FSM) can achieve nondestructive monitoring without punching holes on pipeline. However, the existing equipments with DC FSM have many disadvantages, such as low signal-to-noise ratio, easy cause spark, thick cable and so on. Aiming at these problems, the external monitor system for pipeline internal corrosion based on AC FSM was designed and realized in this paper, which contains hardware subsystem and software subsystem. In hardware subsystem, the AC excitation and lock-in amplifier were adopted. firstly, preamplifing the weak voltage signal collected from the probes installed on the outer wall of the pipeline, then lock-in amplifier was used to remove all the other interference with different frequencies to ensure the desired signal can be extracted. In software subsystem, the data acquisition and analysis software was designed and developed, the function of 2-D display and 3-D display of data were realized. The Experiments and field application show that the equipment meets the monitoring demands.