## 5.6.6 AxisInformation

This structure defines the information for auxiliary axis for ArrayItemType Variables.

There are three typical uses of this structure:

1. The step between points is constant and can be predicted using the range information and the number of points. In this case, axisSteps can be set to NULL.
2. The step between points is not constant, but remains the same for a long period of time (from acquisition to acquisition for example). In this case, axisSteps contains the value of each step on the axis.
3. The step between points is not constant and changes at every update. In this case, a type like XYArrayType shall be used and axisSteps is set to NULL. Its elements are defined in Table 23.

Table 23 – AxisInformation DataType structure

Name Type Description
AxisInformation structure
engineeringUnits          EUInformation Holds the information about the engineering units for a given axis.
eURange          Range Limits of the range of the axis
title          LocalizedText User readable axis title, useful when the units are %, the Title may be “Particle size distribution”
axisScaleType          AxisScaleEnumeration LINEAR, LOG, LN, defined by AxisSteps
axisSteps          Double[] Specific value of each axis steps, may be set to “Null” if not used

Its representation in the AddressSpace is defined in Table 24.

Table 24 – AxisInformation definition

Attribute Value
BrowseName AxisInformation
IsAbstract False

Subtype of Structure defined in OPC 10000-5.

References NodeClass BrowseName DataType TypeDefinition Other
Conformance Units
Data Access AxisInformationType

When the steps in the axis are constant, axisSteps may be set to “Null” and in this case, the Range limits are used to compute the steps. The number of steps in the axis comes from the parent ArrayItem.ArrayDimensions.