If the transducer gain(H) has units of V/cm, the units for repeatable error(RE) become cm.
To regulate system output accurately requires that the open-loop gain be large enough.
However, the open-loop gain is limited by the component of the loop having the lowest natural frequency.
Since hydraulic oil(although highly incompressible) is more compressible than steel, the oil under compression is the lowest natural frequency component.
The following equation allows for the calculation of the natural frequency of the oil behaving as a spring-mass system