Which type of testing is associated with low frequencies below 500 Hz?

Displacement testing is the correct choice when dealing with vibrations at low frequencies below 500 Hz because it measures the physical movement of an object. At these lower frequencies, the motion of the vibrating component can be described effectively in terms of its displacement.

Displacement measurements are particularly relevant in this frequency range since they provide direct insight into how much an object moves during its vibrational cycle. This is crucial for understanding issues such as misalignment, imbalance, and other faults that can lead to operational problems in machinery.

In contrast, velocity testing is typically more applicable in the mid-frequency range, where the oscillatory motion can be analyzed in terms of its rate of change, providing insights into the severity of vibration but not as directly tied to low-frequency behavior. Acceleration testing is primarily used for high-frequency vibrations, as it indicates the rate of change of velocity and may not offer the same clarity of low-frequency movement. Current testing relates to electrical properties and is not a direct measure of vibrational characteristics, making it unrelated to the frequency range in question.

Therefore, displacement testing is specifically tied to the characteristics of low-frequency vibrations and is the appropriate measurement technique in this context.