Abbott Firestone Curve
Also known as a Material Ratio Curve. It is a graph showing the percentage of material that would be present after slicing through the surface at varying depths below the highest peak.
Abbott Firestone Curve is often used on cylinder liners for example to check and predict wear characteristics.
See the parameter Rmr
Amplitude Distribution
Amplitude Distribution is a graph showing the amount of data points of the profile that would be present after slicing through the surface at various depths below the peak. Amplitude Distribution can aid in analysis by showing whether the surface has more peaks or valleys or more valleys that peaks, or an equal amount of both.
See the parameter Rsk
Analogue instrument
This is an instrument that operates with a signal that can vary continuously. Some instruments use analogue electronic signals to represent the profile. On most modern instruments, the signal used for analysis is digital.
Anisotropic Surface
A surface with a directional lay – a visible direction in its roughness.
Arcuate Correction
This is the correction applied to the measured data to compensate for the fact that the stylus (whose arm is pivoted) moves in an arc rather than in a true vertical motion. Not all surface finish instruments have the benefit of arcuate correction. Only when measuring certain types of profile over certain ranges is arcuate correction necessary. Systems that measure form as well as surface finish usually require arcuate correction.
Assessment Length
The data left after filtering used to analyse the surface.
Auto Lift-off
Some instruments have the ability to lift the stylus from the surface after measurement. This can be done by use of mechanisms either on the gauge or by use of a column movement on the instrument. This prevents stylus damage when either moving the stylus back to the start position in the non-measuring direction or for lifting the stylus clear in order to load a new component.
Auto Reverse
A facility to reposition the stylus at the start position automatically after a measurement.
Axis Calibration
For automatic programming and for some types of analysis it is critical that all movement axes (column, arm, and spindle) are capable of being calibrated. If a component is to be measured at known heights then the column on the instrument should have some capability of recording those heights. If horizontal or radial measurements are to be made, then calibration of the instrument’s arm is necessary. Spindle position is critical, especially on roundness instruments and some means of calibrating this is also required.
