Which of the following is not a primary purpose for using an eddy current standard?

The determination of instrument control settings to optimize the performance of the eddy current test system on test specimens is not considered a primary purpose of using an eddy current standard. Instead, the primary purposes revolve around establishing criteria for testing and ensuring the system's reliability and sensitivity.

Utilizing an eddy current standard primarily focuses on validating the system’s capabilities, such as confirming that it can effectively detect discontinuities (which relates to the first purpose), determining whether identified discontinuities warrant rejection based on industry standards (the second purpose), and checking if the sensitivity of the test system maintains its required performance over time (the fourth purpose).

In contrast, setting instrument control settings to maximize passing rates on test specimens is more about operational optimization, rather than a foundational purpose of standards. While control settings are important for effective testing, they do not directly relate to establishing or validating the fundamental capabilities of the eddy current test system. Thus, it diverges from the essential functions that the use of standards is intended to fulfill.