When performing a close interval survey (CIS), good practice has the surveyor using an oscilloscope to obtain a waveform reading. The main purpose of obtaining a waveform is to establish that correctly timed interruption is taking place. However, further analysis in the field or at the office can provide more insight into the rectifier operation and other electronic sources affecting the pipe. Examining frequency analysis using the Fast Fourier Transform (FFT) algorithm provides insights about the frequency of interference. Graphing the FFT results against time can confirm proper interruption in noisy circumstances where simple visual analysis fails.

Subject
Field performance, Materials, Piping, Voltage, Materials performance, Tools, Instrumentation, Algorithms, Transmission lines, Rectifiers, Equipment, Health, safety, and environment, Surveys
Keywords:
close interval survey, waveform, waveform analysis, Fast Fourier Transform, harmonics
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2022
Association for Materials Protection and Performance (AMPP)
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