Vibration

mils peak-to-peak

where mils = thousandsth of an inch = 0.001"

peak-to-peak means total displacement from the 'lowest' point to the 'highest' point

Unlike Thrust Monitoring, It is measured in Peak-Peak. Mils is thousand of an inch.

1 Mil = 0.001 Inches = 25.4 micro meter

Smaller units like micro meter are also used.