Glossary
encoder options
Most of our positioners are available with optional encoders for closed loop control. The encoder
allows to read back the actual position, while a feedback loop integrated into the corresponding
electronics is used to minimize the difference between target position and actual position.
Setpoints can either be defined in a software interface (ANC350, ECC100) or on the front panel
of the closed loop electronics (ANC350). The available encoder types are described below.
/RES: Resistive Encoder
The working principle of this encoder type is based on a potentiometer. It is the method
of choice for applications at cryogenic temperatures, ultra high vacuum and highest mag-
netic fields (current maximum tested field: 31 T). The /RES encoder measurement refers
to the absolute sample position with a position resolution of 200 nm and a repeatability
of 1 μm for most linear steppers. For ultra low temperatures (T < 1 K) a special /RES+ sen-
sor is available which is included in all our /ULT models.
/NUM, /NUM+: Optoelectronic Encoder
The usage of a glass grating and the interpretation of the generated Moiré pattern char-
acterizes 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 room temperature
conditions including /HV and /UHV positioners. The +-version /NUM+ features a reduced
thermal dissipation of only 50 mW making it especially suited for /HV and /UHV position-
ers. The necessary amplifier has been detached from the sensor itself and placed in the
connector of the cable outside of the vacuum chamber. The Premium Line/NUM(+)models
can also be used in high magnetic fields up to 7 T.
/FPS: Combination with Interferometer
Outstanding precision is achieved by combining attocube’s innovative, fiber-based
interferometers (FPS or IDS) with standard open loop positioning stages. A 25 pm position
resolution and 2 nm repeatability even at cryogenic temperatures (/LT, /ULT), UHV
conditions and high magnetic fields outrivals the specifications of any other encoder
type. To achive maximal reproducability the position should be measured as close to
the point of interest as possible. For detailed information on the interferometers,
please refer to http://www.attocube.com/attosensorics/