Scope of Measurement of REDS
The shortest possible explanation of the scope of measurement of REDS can best be illustrated by explaining how REDS measures.
REDS determines imbalances of piston engines by high resolution measurement of the dynamic rotational angular velocity of the crankshaft. Or in other words, torsional vibrations or accelerations and decelerations of the flywheel.
Imbalances are caused by both the thermodynamic processes in the engine, expansion and compression of gases, and (clearances of) moving parts like, for example, bearings.