Which of the following is not a commonly used eddy current testing readout mechanism?

The correct answer identifies a component not traditionally associated with eddy current testing readout mechanisms. In eddy current testing, it is crucial to translate the detected signals into a readable format for analysis, and commonly used devices for this purpose provide immediate visual feedback or recorded data.

A signal generator is employed to create electromagnetic waves but is not a readout mechanism. It serves an important role in generating the current necessary to set up the conditions for the eddy currents in the test object. The readout mechanisms, on the other hand, are designed to display the results of the testing process.

Devices such as meters are often used to directly quantify the response, providing a clear and immediate understanding of the material integrity. Cathode ray tubes, while somewhat outdated now, historically served to visualize the oscillations acquired during eddy current testing. Strip chart recorders were utilized to provide a continuous record of the data over time, making them valuable for ongoing assessments.

In summary, the distinguishing factor is that a signal generator is essential for initiating the testing but is not a mechanism that presents or interprets the results or findings from the test, which is the role of the other listed devices.