The ProcessValueSetpointVariableType is a subtype of 0:AnalogUnitRangeType. It is used to define the desired value of the Variable it belongs to. It is, for example, used by the ProcessValueType, defining the desired value for the 3:AnalogSignal. The DataType, ValueRank and ArrayDimensions shall be identical to the Variable it belongs to. The 0:EngineeringUnits, of that Variable shall have the same Values as defined on the Variable it belongs to. The 0:EURange shall be the same, or further restricted by providing a smaller high or a higher low value. Instances of that VariableType shall not provide the 0:InstrumentRange. A process value setpoint Variable does not require the server to execute any internal logic to bring the process value (Variable to which the process value setpoint belongs) to the process value setpoint.

The VariableType is formally defined in Table 6.

Table 6 – ProcessValueSetpointVariableType Definition

Attribute	Value
BrowseName	ProcessValueSetpointVariableType
IsAbstract	False
ValueRank	-2 (-2 = Any)
DataType	Number
Description	Define the desired value of the Variable it belongs to.
References	Node Class	BrowseName	DataType	TypeDefinition	Other
Subtype of the 0:AnalogUnitRangeType
0:HasComponent	Variable	SubstituteValue	0:Number{Any}	0:BaseDataVariableType	O
0:HasComponent	Variable	LowLowDeviation	0:Number	0:AnalogUnitType	O
0:HasComponent	Variable	LowDeviation	0:Number	0:AnalogUnitType	O
0:HasComponent	Variable	HighDeviation	0:Number	0:AnalogUnitType	O
0:HasComponent	Variable	HighHighDeviation	0:Number	0:AnalogUnitType	O
0:HasProperty	Variable	AutoDeviationAdjustment	0:Boolean	0:PropertyType	O
0:HasComponent	Variable	DeviationSensitivity	0:UInt16	0:MultiStateValueDiscreteType	O
Conformance Units
Machinery Process Values Base Types
Machinery Process Values Base SetpointType

The optional SubstituteValue Variable provides a value that should be used when the process value setpoint cannot be controlled anymore. This specification does not define, when this is the case. There might be, for example, a connection lost from the controlling device. The SubstituteValue shall have the same DataType, ValueRank and ArrayDimensions as the process value setpoint Variable. The same meta data as defined for the process value setpoint Variable apply.

There are four optional deviation Variables: LowLowDeviation, LowDeviation, HighDeviation and HighHighDeviation. They define different limits for deviation. The deviation considered is between the value of the process value setpoint and the value of the Variable to which the process value setpoint belongs. The deviation limits are defined relative to the process value setpoint. It is not required to provide all deviation Variables. For example, a process value may only have a LowDeviation. The deviation can either be defined in percentage or absolute.

• If the deviation is defined in percentage, the 0:EngineeringUnits shall be percentage (UnitId: 20529 with NamespaceUri http://www.opcfoundation.org/UA/units/un/cefact). The percentage value is calculated by the range of values between the high and the low limit. 100% therefore corresponds to the equation "EURange.High minus EURange.Low".
• If the deviation is defined absolute, the 0:EngineeringUnits shall be the same as the process value setpoint.

If one deviation Variable is defined in percentage, all deviation Variables shall be defined in percentage.

All instances of the ProcessValueSetpointVariableType providing any of the deviation Variables shall have scalar Values. Subtypes may be created using arrays and defining the expected behaviour with respect to the deviation Variables.

The deviation Variables are defined in an order. The LowLowDeviation shall be smaller or equal LowDeviation, which shall be smaller or equal zero. HighHighDeviation shall be larger or equal HighDeviation, which shall be larger or equal to zero.

In Figure 7, the relation of the deviation Variables, the ProcessValueSetpoint, and the ranges is shown. The deviation Variables are relative to the ProcessValueSetpoint, whereas the ranges are absolute. In Figure 7, the ProcessValueSetpoint changes at some point in time, and therefore the absolute value for the deviation. Note, that a change of the ProcessValueSetpoint may lead to the absolute value of a deviation may pass the ranges.

Figure 7 – Relation between deviation Variables, ranges, process value setpoint and current Value

Note that Servers may generate 0:DeviationAlarms (see 7.1) when the deviation limits are reached. The deviation Variables are used to configure this alarm.

The optional AutoDeviationAdjustment Variable defines if the deviation Variables are automatically adjusted based on the settings of DeviationSensitivity (if provided) in case the configuration has changed (0:EURange or DeviationSensitivity). If set to TRUE, the deviation Variables shall be automatically adjusted and writing the deviation Variables shall fail.

The optional DeviationSensitivity Variable indicates the sensitivity of the deviation Variables when automatically set. This specification defines standardized 0:EnumValues (see Table 7) that shall be used as defined in this specification or omitted. Servers may define additional 0:EnumValues starting with 256.

Note that the predefined 0:EnumValues (FINE, MIDDLE, and ROUGH) do not define the absolute widths of the set deviation bands, they are device dependent.

The child Nodes of the ProcessValueSetpointVariableType have additional Attribute values defined in Table 7.

Table 7 – ProcessValueSetpointVariableType Attribute values for child Nodes

BrowsePath	Value Attribute	Description Attribute
LowLowDeviation	-	Defines the low low limit for deviation, relative to the process value setpoint.
LowDeviation	-	Defines the low limit for deviation, relative to the process value setpoint.
HighDeviation	-	Defines the high limit for deviation, relative to the process value setpoint.
HighHighDeviation	-	Defines the high high limit for deviation, relative to the process value setpoint.
AutoDeviationAdjustment	-	Defines if the deviation variables are automatically adjusted.
DeviationSensitivity	-	Indicates the sensitivity of the deviation variables when automatically set.
SubstituteValue	-	Value that should be used when the process value setpoint cannot be controlled anymore.
DeviationSensitivity 0:EnumValues	{{0, FINE, tight tolerances}, {1, MIDDLE, mean tolerances}, {2, ROUGH, large tolerances}}	-