Aerotech QNP3 Series Hardware Manual page 53

QNP3 Hardware Manual
Accuracy is defined as the measured peak-peak error (reported in units of micrometers, nanometers,
etc.) from the nominal commanded position that results from a positioning stage as it is commanded to
move bidirectionally throughout travel.
Linearity is defined as the maximum deviation from a best-fit line of the position input and position output
data. Linearity is reported as a percentage of the measurement range or travel of the positioning stage.
An example of the raw measurement results from an accuracy and linearity test is shown in
accuracy plot is shown in
in the data. The deviation of a best-fit line to the measurement data taken in
the linearity error. The residuals from this best-fit line and an illustration of how linearity error is calculated is
shown in Figure C-9.
In conclusion, the term accuracy is used to quantify both sensitivity effects (slope of measured versus
actual position) as well as nonlinearities in positioning and is reported as a pk-pk value. The term linearity is
used to quantify the effects of nonlinearities in positioning only and is reported as a maximum error or
deviation of the residuals from the best fit line through the measured versus actual position data. The
positioning accuracy can be approximated from the linearity specification by doubling the linearity
specification. For example, a 0.02% linearity for a 100 μm stage is a 20 nm maximum deviation. The
approximated accuracy error is 2 x 20 nm or 40 nm pk-pk.
Figure C-7: Raw measurement results from an accuracy and linearity test of a 100 μm piezo
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Figure C-8. Notice how the accuracy results have a small residual slope remaining
Appendix C
Piezo Engineering Tutorial
Figure C-7
stage
Figure C-7. The
is used to calculate
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