Glossary
sensor terminology
Sensor Resolution Sensor Repeatability
The term sensor resolution or sensitivity indicates the smallest incre-
mental position change detectable by a sensor. If the sensitivity is not
fundamentally limited due to mechanical properties such as friction,
the sensitivity is almost always bandwidth dependent. attocube speci-
fies the resolution of optoelectronic /NUM(+) sensors at a measurement
bandwidth of 1 kHz. The sensor repeatability represents the position error when repeatedly
approaching a certain sensor value from both sides (bi-directional
repeatability, e.g. /NUM, /NUM+), respectively one side (uni-directional
repeatability, e.g. /RES).
Sensor Accuracy
The term sensor accuracy represents the absolute deviation of any
measurement from a calibrated, metrologically traceable standard.
Best accuracy is often obtained by interferometric sensors, using
well-known laser lines from thermally stabilized single mode gas lasers.
Sensor accuracy does not necessarily relate to sensor sensitivity and
repeatability, i.e. a sensor may provide a very high sensitivity and
repeatability, yet lack a high accuracy and vice versa. attocube’s FPS
and IDS interferometric displacement sensors were tested by
Germany’s national metrology institute PTB. The accuracy of both
sensors was measured to be smaller than 0.2 ppm. They can be
combined with the attoMOTION piezostages for the ultimate accuracy
and resolution.
At attocube, the sensor repeatability is measured in conjunction with
an actual positioner, i.e. parameters such as minimum step size, ther-
mal expansion, and resolution all contribute to the sensor repeatabil-
ity. The repeatability for each closed loop positioner is determined by
the value of the standard deviation (σ). An example of a repeatability
measurement is given in the figure below.
attoMOTION
Piezo-based Nano Drives
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