Which of the following could help suppress unwanted high-frequency harmonics?

A low pass filter is designed to allow low-frequency signals to pass through while attenuating (reducing the amplitude of) frequencies higher than a certain cutoff frequency. This characteristic makes it particularly effective for suppressing unwanted high-frequency harmonics that may interfere with the desired signal in eddy current testing. High-frequency noise can mask important signals that convey the integrity or characteristics of the material being examined. By employing a low pass filter, operators can improve the clarity of the data being analyzed, leading to more accurate results.

In the context of eddy current testing, the suppression of high-frequency harmonics is essential for improving signal quality. While an oscillator generates signals at specific frequencies and a phase discriminator separates signals based on their phase, they do not function to mitigate unwanted harmonic content. Similarly, a high pass filter would instead allow high-frequency signals to pass while attenuating lower frequencies, which is contrary to the requirement of suppressing high-frequency harmonics. Thus, the low pass filter is the appropriate choice for this purpose.