What unit is mm/s2 read in?

The unit mm/s² refers to millimeters per second squared, which is a measurement of acceleration. In vibration analysis, particularly in the context of how vibration data is recorded and interpreted, acceleration is often quantified using the root mean square (RMS) value to provide a meaningful representation of the vibration's intensity. The RMS value helps in assessing the effective value of a varying signal, providing an average level that correlates with the potential impact on machinery and structure. Therefore, mm/s² can be interpreted within the context of this RMS measurement method, making the correct answer RMS.

This context underlines why other options do not apply: PK (peak) is a different measurement that refers to the maximum amplitude of the vibration signal, while Imperial and Standard refer to systems of measurement (Imperial being a system primarily used in the United States, and Standard typically referring to the metric system) rather than specific methods for interpreting acceleration in vibration analysis.