Glossary encoder options
Sensor Resolution
The term sensor resolution or sensitivity indicates the smallest incremental 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 specifies the resolution of optoelectronic / NUM (+) sensors at a measurement bandwidth of 1 kHz .
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 .
Sensor Repeatability
The sensor repeatability represents the position error when repeatedly approaching a certain sensor value from both sides . At attocube , the sensor repeatability is measured in conjunction with an actual positioner , i . e . parameters such as minimum step size , thermal expansion , and resolution all contribute to the sensor repeatability . 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 .
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/ NUM , / NUM +: Optoelectronic Encoder |
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ECC100
ANC350
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12 contacts |
Grating Optochip |
The usage of a glass grating and the interpretation of the generated Moiré pattern characterizes the working principle of the / NUM and / NUM + encoder . The measurement refers to the relative sample position with a position resolution of 1 nm and a repeatability of typically 50 nm for most linear stepping positioners . An absolute position information is also available via a reference mark . This encoder is available for all Industrial Line positioners including / HV and / UHV types . The + -version / NUM + features a reduced thermal dissipation of only 50 mW making it especially suited for / HV and / UHV positioners . The necessary amplifier has been detached from the sensor itself and placed in the connector of the cable outside of the vacuum chamber .
attoMOTION
Piezo-based Nano Drives
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