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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