Which of the following methods can improve the signal-to-noise ratio in an eddy current test system?

Improving the signal-to-noise ratio (SNR) in an eddy current testing system is critical for enhancing the quality of the results obtained. Each of the methods listed contributes to this improvement.

Filtering or differentiation helps eliminate unwanted noise from the signal by focusing on the frequencies of interest. This method can either amplify desired signals while suppressing noise or mathematically differentiate the signal to enhance relevant features.

Phase discrimination allows for distinguishing between signals based on their phase characteristics. By analyzing the phase relationship between the reference signal and the obtained signal, it becomes possible to enhance the detection of flaws or features of interest, thus improving the SNR.

Integration is also a technique that can be applied, particularly in the post-processing stage, where it combines multiple readings over time to create a more stable and higher quality signal. This cumulative effect reduces noise by averaging out random fluctuations that do not correlate with the actual signal being observed.

Since all these methods play a role in improving the signal-to-noise ratio, it is correct that the choice encompassing all of the methods is indeed the best answer. Each method contributes to filtering out noise and enhancing the clarity of the signals detected in eddy current testing.