3.3.1.44. NXpositioner

Status:

base class, extends NXobject

Description:

A generic positioner such as a motor or piezo-electric transducer.

Symbols:

No symbol table

Groups cited:

NXtransformations

Structure:

@default: (optional) NX_CHAR

Declares which child group contains a path leading ...

Declares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

name: (optional) NX_CHAR

symbolic or mnemonic name (one word)

description: (optional) NX_CHAR

description of positioner

value: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_ANY}

best known value of positioner - need [n] as may be scanned

raw_value: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_ANY}

raw value of positioner - need [n] as may be scanned

target_value: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_ANY}

targeted (commanded) value of positioner - need [n] as may be scanned

tolerance: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_ANY}

maximum allowable difference between target_value and value

soft_limit_min: (optional) NX_NUMBER {units=NX_ANY}

minimum allowed limit to set value

soft_limit_max: (optional) NX_NUMBER {units=NX_ANY}

maximum allowed limit to set value

velocity: (optional) NX_NUMBER {units=NX_ANY}

velocity of the positioner (distance moved per unit time)

acceleration_time: (optional) NX_NUMBER {units=NX_ANY}

time to ramp the velocity up to full speed

controller_record: (optional) NX_CHAR

Hardware device record, e.g. EPICS process variable, taco/tango …

depends_on: (optional) NX_CHAR

NeXus positions components by applying a set of translations and rotations ...

NeXus positions components by applying a set of translations and rotations to apply to the component starting from 0, 0, 0. The order of these operations is critical and forms what NeXus calls a dependency chain. The depends_on field defines the path to the top most operation of the dependency chain or the string “.” if located in the origin. Usually these operations are stored in a NXtransformations group. But NeXus allows them to be stored anywhere.

TRANSFORMATIONS: (optional) NXtransformations

This is the group recommended for holding the chain of translation ...

This is the group recommended for holding the chain of translation and rotation operations necessary to position the component within the instrument. The dependency chain may however traverse similar groups in other component groups.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/nexusformat/definitions/blob/main/base_classes/NXpositioner.nxdl.xml