Repeatability
This is how closely a system can return to the same position or the same speed when the same command is given over and over. It should not be confused with accuracy: a system may deviate from the target, but if it deviates by the same amount every time, its repeatability is high and that deviation can be removed by calibration.
Measurement is simple: the same command is given dozens of times and the spread of the values reached is examined. The result is given as a percentage of full scale or directly in physical units such as degrees or millimeters. The main factors that degrade repeatability are:
- Valve hysteresis and spool friction.
- Oil temperature changing over the cycle and viscosity drifting.
- Mechanical play: a loose mounting clamp, a worn pin, a connection with movement in it.
- Signal noise in the remote control and drift of the joystick center.
In automatic cycles, repeatability matters more than accuracy; because you can correct a constant deviation by applying an offset in the controller, but you cannot correct a random spread. AXI's retrofit kits typically specify ±1° position accuracy; to hold that value in the field, the mounting clamp must be genuinely tight and the lever must not move with vibration.
Where this term is used: What Is a Hydraulic Lever Retrofit Kit? Definition, Components, Operating Principle