Blow-by effect
"Blowing past" a piston seal. With large pressure gradients it can occur that the seal is not pressed against the sealing surface, instead it is pressed into the grove (Figure B 21) .
Differential cylinder
Double-acting cylinder with one-sided piston rod in which the ratio of the piston area AK to the annular area on the piston rod side is essential for the function of the fluid-related circuit (CETOP RP100) [...] as large as possible. The different size areas signify different velocities in the flow and return with the same Q: The ratio of the two areas is termed the ratio of piston areas α.
Quiescent flow
) and is pressure-controlled. With servo valves , the quiescent flow comprises the flow for the first stage and the leakage for the second stage. It changes in line with the inlet pressure and the input
Wetting ability
to cover the surface over which it is distributed to a greater or lesser degree. Hydraulic fluids with good wetting ability adhere better to the surface. As a consequence the lubricating film has better [...] better load bearing in the boundary layer area. This aspect is particularly important for seals where with poor wetting ability the lubricating film is pressed away at the sealing surfaces such that dry friction
Pre-fill valve
fill the cylinder chamber behind a piston moving rapidly under its own weight or with a piston for rapid traverse with unpressurised oil from the tank. The high velocity required produces very high flow
Measured value
for the measured variable. Compared with the correct value for the measured variable — the input variable for the measuring device — the measured value is associated with errors caused, for example, by an
Instability of a control system
generally a transfer element with an input variable and an output variable is referred to as unstable (not stable from a transmission perspective) if the output variable associated with each restricted input
Digital signals
Discrete signals with a finite number of value ranges for the signal parameter where each value range is assigned as a whole to a specific item of information. Digital signals can also have multiple parameters [...] parameters (DIN 19 226). In control technology digital signals are only used with two value ranges ( binary signals ). A digital signal comprises several parallel binary signals (Figure D 27 a) that combined
Monitoring
Review of certain variables in terms of complaints with predetermined values, ranges or switching states. The variables to be monitored can be measured directly or may be the result of an evaluation (DIN [...] in which the desired state is saved and which issues an assessment of the state through comparisons with the actual values ( Figure U 12 ). Thus monitoring is a prerequisite for identifying damage at an
Digital control
within the signal processing with digital signals and that primarily processes numerically represented signals (Figure D 28) . The signal processing is undertaken primarily with digital function units, such