1 Scope

The OPC UA for Machinery specification contains various building blocks for Machinery that allow to address use cases across different types of machines and components of machines defined in various companion specifications.

For the general scope of the OPC UA for Machinery specification see OPC 40001-1.

This part contains a building block for

Process Values

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments and errata) applies.

OPC 10000-1, OPC Unified Architecture - Part 1: Overview and Concepts

OPC 10000-1

OPC 10000-3, OPC Unified Architecture - Part 3: Address Space Model

OPC 10000-3

OPC 10000-4, OPC Unified Architecture - Part 4: Services

OPC 10000-4

OPC 10000-5, OPC Unified Architecture - Part 5: Information Model

OPC 10000-5

OPC 10000-6, OPC Unified Architecture - Part 6: Mappings

OPC 10000-6

OPC 10000-7, OPC Unified Architecture - Part 7: Profiles

OPC 10000-7

OPC 10000-8, OPC Unified Architecture - Part 8: Data Access

OPC 10000-8

OPC 10000-9, OPC Unified Architecture - Part 9: Alarms and Conditions

OPC 10000-9

OPC 10000-100, OPC Unified Architecture - Part 100: Devices

OPC 10000-100

OPC 40001-1, OPC UA for Machinery - Part 1: Basic Building Blocks

http://www.opcfoundation.org/UA/Machinery/

OPC 30081, OPC UA for Process Automation Devices – PA-DIM^TM

http://www.opcfoundation.org/UA/PADIM/

3 Terms, definitions and conventions

3.1 Overview

It is assumed that basic concepts of OPC UA information modelling are understood in this specification. This specification will use these concepts to describe the Machinery – Process Values Information Model. For the purposes of this document, the terms and definitions given in OPC 10000-1, OPC 10000-3, OPC 10000-4, OPC 10000-5, OPC 10000-7, OPC 10000-9, OPC 40001-1, as well as the following apply.

Note that OPC UA terms and terms defined in this specification are italicized in the specification.

3.2 OPC UA for Process Values terms

No additional terms defined in this specification.

3.3 Abbreviated terms

3.4 Conventions used in this document

For conventions used in this document see OPC 40001-1.

4 General information to Machinery and OPC UA

For general information to Machinery and OPC UA see OPC 40001-1.

5 Use cases

The purpose of this specification is to provide the mechanisms related to the representation of process values for domain-specific Companion Specifications. Accordingly, a number of use cases must be satisfied in this model:

The user would like to access the process values of a machine and its various meta data like ranges, precision and unit.

The user would like to access and set the setpoints of the process values of a machine.

The user would like to access and set deviation limits of the process values, relative to the setpoints.

The user would like to get informed when a process value is passing a deviation limit or range.

The user would like to get the percentage value of a process variable, also when there are dynamic ranges.

The user would like to zero-point adjust the current value of a process value.

The user would like to get vendor-specific error codes on devices providing process values.

The user would like to access and set a substitution value in case of connections lost.

The user would like to get identification information of devices providing process values.

The user would like to get information about the health status of devices providing process values.

6 Process Values Information Model overview

6.1 General

This information model provides information about process values, for example provided by actuators or sensors. In 6.2, the integration of such devices as components of a machine is described. This includes information about the identification of a device as well as health information and specific errors. In 9.1, the VariableType representing process value setpoints is introduced. In 6.4, an ObjectType using the VariableType and providing the process value as well as adding additional mechanisms for alarming and zero-point adjustment is described. Examples of the overall usage of process values are described in 6.5.

6.2 Integration as Device in Machinery Specification

In order to integrate process values in the Machinery Information Model including device information, the device should be represented as component of a machine. An example ObjectType X:MySensorType is shown in Figure 1. It provides identification information using the 4:MachineryComponentIdentificationType. The process values – a device can potentially provide more than one process value – are grouped by the 3:SignalSet defined in the 3:ISignalSetType of OPC 30081. To provide the overall health status of the device as well as specific errors, the 2:IDeviceHealthType is implemented, defined in OPC 10000-100.

Note that it is not required to provide any device information to use the process values defined in this specification. However, this mechanism provides information about the identification and health status of the device.

6.3 ProcessValueSetpointVariableType

In Figure 2, illustrates the 3:AnalogSignalVariableType and the ProcessValueSetpointVariableType and their supertypes with key InstanceDeclarations. The 3:AnalogSignalVariableType provides the optional Properties 0:ValuePrecision and 0:InstrumentRange and the mandatory Properties 0:EURange and 0:EngineeringUnits and are used as defined in OPC 10000-8. They provide information about the precision, ranges and unit of the process value. The optional Variables 3:ActualValue, 3:SimulationValue, and 3:SimulationState are used as defined in OPC 30081 and provide a simulation value and a flag to define, which value is used.

The ProcessValueSetpointVariableType defined in 9.1 adds additional, optional meta data.

6.4 ProcessValueType

In Figure 3, the ProcessValueType and its supertypes with key InstanceDeclarations is shown. The mandatory 3:SignalTag contains a unique name as defined by OPC 30081. The optional 3:ZeroPointAdjustment Method allows to set a zero point as defined in OPC 30081. The ProcessValueType adds a reference to the ZeroPointAdjustmentEventType. Events of this EventType are generated, when the zero-point adjustment is executed (see 8.1). The 3:AnalogSignal defined in OPC 30081 is extended with additional meta data. The ProcessValueType is defined in 7.1, having additional optional components like process value setpoint and alarm information.

This ObjectType was introduced to bind functionality to the process value that cannot be added to the 3:AnalogSignal directly, like Objects and Methods.

6.5 Examples applying Process Values

In Figure 4, an example of applying the device values in a machine is given, providing all information defined in this specification. The X:MyMachine Object contains a X:Sensor1 in its 4:Components folder. The X:Sensor1 provides identification information and health status. In addition, it contains two process values, X:Temperature and X:Pressure. Those Objects can be referenced from other paths as well, like the X:Monitoring Object of X:MyMachine. The X:Pressure Object contains various capabilities like the 3:ZeroPointAdjustment Method, DeviationAlarm, and the 3:AnalogSignal containing the process value. This Variable contains various sub-variables with meta data for ranges and unit, deviation etc.

In Figure 5, an example is given using the base infrastructure defined in this specification to provide process values. In this case, no device information or the optional information is given, the X:MyMachine just provided some process values under the X:Monitoring Object.

6.6 Defining Setpoints without an associated Process Value

The ProcessValueType is designed to represent a process value having optionally a process value setpoint. It is not designed to represent a setpoint without a process value. If a setpoint without an associated process values should be represented, using the ProcessValueType is inappropriate. Information models may use the ProcessValueSetpointVariableType as representation of a setpoint. But also this VariableType has optional subvariables that imply a process value (everything associated to deviation) that should not be used without an associated process value.

7 OPC UA ObjectTypes

7.1 ProcessValueType ObjectType Definition

The ProcessValueType represents a process value. It is formally defined in Table 1.

This ObjectType inherits the InstanceDeclarations defined on its supertypes, including the mandatory 3:SignalTag as defined in OPC 30081.

The mandatory 3:AnalogSignal Variable is overridden and additional InstanceDeclarations are added (see Table 2). It contains the process value and meta data about the process value.

The 3:AnalogSignalVariableType already provides the mandatory 0:EURange, 0:EngineeringUnits and the optional 0:ValuePrecision, 0:InstrumentRange, 3:ActualValue, 3:SimulationValue and 3:SimulationState as defined in OPC 10000-8 and OPC 30081.

The PercentageValue Variable on the 3:AnalogSignal provides the process value in percentage. The 0:EngineeringUnits of the Variable shall always be percentage (UnitId: 20529 with NamespaceUri http://www.opcfoundation.org/UA/units/un/cefact). This Variable is especially useful when the ranges for calculating the percentage values are dynamic, so that the client cannot calculate the percentage based on the 0:EURange of the 3:AnalogSignal Variable. As an example, the wear of a filter should be exposed, by providing the differential pressure. The pressure is presented as the 3:AnalogSignal and the wear is presented as the PercentageValue. Suction output is an internal value. However, the differential pressure depends on the suction output. With 50% suction output the differential pressure of 250 Pa is 0% wear (meaning new filter), for 100% suction output it is 500 Pa and 0% wear. For a used filter, the values are 1600 Pa and 60% wear for 50% suction output and 1700 Pa and 60% wear for 100% suction output. A filter to be replaced would have 2500 Pa and 100% wear for 50% suction output and 2500 Pa and 100% wear for 100% suction output.

There are four optional limit Variables on 3:AnalogSignal: LowLowLimit, LowLimit, HighLimit and HighHighLimit. They define different limits for the Value of the Variable, either absolute or in percentage. It is not required to provide all limit Variables. For example, a process value may only have a LowLimit.

If the limit 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 limit is defined absolute, the 0:EngineeringUnits shall be the same as for the Variable.

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

For all instances of ProcessValueType having an 3:AnalogSignal providing any of the limit Variables, the 3:AnalogSignal shall have scalar Values. Subtypes may be created using arrays and defining the expected behaviour with respect to the limit Variables.

The limit Variables are defined in an order. The LowLowLimit shall be smaller or equal LowLimit, which shall be smaller or equal HighLimit, which shall be smaller or equal HighHighLimit.

In Figure 6, the relation of the limit Variables, and the ranges is shown. The limit Variables are absolute, as well as the ranges.

Note that Servers may generate 0:LimitAlarms when the deviation limits are reached. The limit Variables are used to configure this alarm.

The optional ProcessValueSetpoint Variable provides the desired value of the 3:AnalogSignal. The Server may, or may not control the Value to reach the process value setpoint. The DataType, ValueRank and ArrayDimensions shall be the same as for the 3:AnalogSignal. The 0:EngineeringUnits Property shall have the same Value as the 0:EngineeringUnits Property of 3:AnalogSignal. The 0:InstrumentRange Property, if provided, shall have the same Value as the 0:InstrumentRange Property of 3:AnalogSignal. The 0:EURange Property shall have the same Value as the 0:InstrumentRange Property of 3:AnalogSignal, or further restrict the range, i.e. it may have a larger low and a smaller high value.

The optional 3:ZeroPointAdjustment Method is overridden and works as defined in OPC 30081. The ProcessValueType adds a 0:GeneratesEvent Reference to the ZeroPointAdjustmentEventType. When the Method is called and the execution of the Method starts, a corresponding Event is generated. Such an Event shall not be generated, when the Method was called but execution was not started, for example due to access restrictions or invalid input arguments.

The optional DeviationAlarm Object becomes active, when the process value deviates from the ProcessValueSetpoint. The limits of the DeviationAlarm are bound to the deviation Variables of the ProcessValueSetpoint. As the deviation Variables of the ProcessValueSetpoint may be defined in percentage the limits of the DeviationAlarm may need to be calculated accordingly. The 0:LowLowLimit shall be mapped to LowLowDeviation, 0:LowLimit to LowDeviation, 0:HighLimit to HighDeviation and 0:HighHighLimit to HighHighDeviation. If a deviation Variable is not present, the corresponding limit shall not be provided as well. If no deviation Variable is present, the DeviationAlarm shall not be provided.

The optional LimitAlarm Object becomes active, when the process value reaches a limit. The limits of the LimitAlarm are bound to the limit Variables of the 3:AnalogSignal. As the limit Variables of the ProcessValueSetpoint may be defined in percentage the limits of the DeviationAlarm may need to be calculated accordingly. The 0:LowLowLimit shall be mapped to LowLowLimit, 0:LowLowLimit to LowLimit, 0:HighLimit to HighLimit and 0:HighHighLimit to HighHighLimit. If a limit Variable is not present, the corresponding limit shall not be provided as well. If no limit Variable is present, the LimitAlarm shall not be provided.

The optional Status Variable indicates if a deviation limit or an absolute limit has been reached. This specification defines standardized 0:EnumValues (see Table 3) that shall be used as defined in this specification or omitted. Servers may define additional 0:EnumValues starting with 256. The deviation Variables uses the deviation Variables of the ProcessValueSetpoint, and the limit Variables of the 3:AnalogSignal.

For the standardized 0:EnumValues there is a priority, which value shall be reported, when several limits are reached. If the HighHighLimit or the LowLowLimit is reached, it shall be reported. If those are not reached, but the HighLimit or LowLimit is reached, it shall be reported. If those are not reached, but the HighHighDeviation or LowLowDeviation is reached, it shall be reported. If those are not reached, but the HighDeviation or LowDeviation is reached, it shall be reported. If there are additional 0:EnumValues defined, the priority of those is not defined, and they could be reported instead of the standardized ones.

The optional AlarmSuppression Variable indicates if alarms based on the Status shall be suppressed. This might be useful for example when starting a machine Alarms include but are not limited to OPC UA Alarms, they can for example also be acoustic or visual indications on the machine. This specification defines standardized 0:EnumValues (see Table 3) that shall be used as defined in this specification or omitted. Servers may define additional 0:EnumValues starting with 256.

The components of the ProcessValueType have additional subcomponents which are defined in Table 2.

The child Nodes of the ProcessValueType have additional Attribute values defined in Table 3.

The components of the ProcessValueType have additional references which are defined in Table 4.

8 OPC UA EventTypes

8.1 ZeroPointAdjustmentEventType ObjectType Definition

The ZeroPointAdjustmentEventType provides information, that a zero-point adjustment took place. It is formally defined in Table 5.

This EventType inherits all Properties of the BaseEventType. The 0:SourceNode and 0:SourceName shall be set to the Object the zero-adjustment is bound to (like instances of the ProcessValueType). The 0:Time shall be set to when the zero-point-adjustment took place.

The mandatory ZeroPointAdjustmentResult Variable reflects if the zero-point adjustment was successful. If it was triggered by a Method call, it shall contain the return StatusCode of the Method call.

9 OPC UA VariableTypes

9.1 ProcessValueSetpointVariableType VariableType Definition

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.

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.

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.

10 Profiles and Conformance Units

10.1 Conformance Units

This chapter defines the corresponding Conformance Units for the OPC UA Information Model for Machinery – Process Values.

10.2 Profiles

10.2.1 Profile list

Table 9 lists all Profiles defined in this document and defines their URIs.

10.2.2 Server Facets

10.2.2.1 Overview

The following sections specify the Facets available for Servers that implement the Machinery – Process Values companion specification. Each section defines and describes a Facet or Profile.

10.2.2.2 Machinery-Process Values Base Server Facet

Table 10 defines a Facet that describes the base functionality to provide process values.

10.2.2.3 Machinery-Process Values Simple Device Info Server Facet

Table 11 defines a Facet that describes the base functionality to provide process values in the context of the device / component providing the process value. The identification of the device has to be included, optionally health information can be provided.

10.2.2.4 Machinery-Process Values Zero Point Adjustment Base Server Facet

Table 12 defines a Facet that a server can provide zero point adjustment functionality on a process value.

10.2.2.5 Machinery-Process Values Zero Point Adjustment Events Server Facet

Table 13 defines a Facet that a server can provide zero point adjustment on a process value including the generation of events when the adjustment is executed.

10.2.2.6 Machinery-Process Values Simulation Server Facet

Table 14 defines a Facet that a server can provide process values including simulation values.

10.2.2.7 Machinery-Process Values Base Process Value Setpoint Server Facet

Table 15 defines a Facet that a server can provide process values including a process value setpoint.

10.2.2.8 Machinery-Process Values Percentage Value Server Facet

Table 16 defines a Facet that a server can provide process values including a percentage value.

10.2.2.9 Machinery-Process Values Deviation Base Server Facet

Table 17 defines a Facet that a server can provide process values including deviation limits.

10.2.2.10 Machinery-Process Values Deviation AutoAdjustment Server Facet

Table 18 defines a Facet that a server can provide process values including at least one deviation limit with automatic adjustment. Optionally, the sensitivity of the adjustment is provided.

10.2.2.11 Machinery-Process Values Deviation Monitoring Server Facet

Table 19 defines a Facet that a server can provide process values including deviation limits and a variable to monitor if the deviation limit is reached.

10.2.2.12 Machinery-Process Values Deviation Alarm Server Facet

Table 20 defines a Facet that a server can provide process values including deviation limits and alarms if the deviation limit is reached. Optionally the alarm is represented as Object in the AddressSpace.

10.2.2.13 Machinery-Process Values Deviation Alarm Suppression Server Facet

Table 21 defines a Facet that a server can provide process values including deviation limits and the possibility to supress alarming when the limit is reached.

10.2.2.14 Machinery-Process Values Limits Base Server Facet

Table 22 defines a Facet that a server can provide process values including deviation limits.

10.2.2.15 Machinery-Process Values Limits Monitoring Server Facet

Table 23 defines a Facet that a server can provide process values including absolute limits and a variable to monitor if the absolute limit is reached.

10.2.2.16 Machinery-Process Values Limits Alarm Server Facet

Table 24 defines a Facet that a server can provide process values including absolute limits and alarms if the absolute limit is reached. Optionally the alarm is represented as Object in the AddressSpace.

10.2.2.17 Machinery-Process Values Limits Alarm Suppression Server Facet

Table 25 defines a Facet that a server can provide process values including absolute limits and the possibility to supress alarming when the limit is reached.

10.2.3 Client Facets

10.2.3.1 Overview

This specification does not define any Facets for Clients.

11 Namespaces

11.1 Namespace Metadata

Table 26 defines the namespace metadata for this document. The Object is used to provide version information for the namespace and an indication about static Nodes. Static Nodes are identical for all Attributes in all Servers, including the Value Attribute. See OPC 10000-5 for more details.

The information is provided as Object of type NamespaceMetadataType. This Object is a component of the Namespaces Object that is part of the Server Object. The NamespaceMetadataType ObjectType and its Properties are defined in OPC 10000-5.

The version information is also provided as part of the ModelTableEntry in the UANodeSet XML file. The UANodeSet XML schema is defined in OPC 10000-6.

Note: The IsNamespaceSubset Property is set to False as the UANodeSet XML file contains the complete Namespace. Servers only exposing a subset of the Namespace need to change the value to True.

11.2 Handling of OPC UA Namespaces

Namespaces are used by OPC UA to create unique identifiers across different naming authorities. The Attributes NodeId and BrowseName are identifiers. A Node in the UA AddressSpace is unambiguously identified using a NodeId. Unlike NodeIds, the BrowseName cannot be used to unambiguously identify a Node. Different Nodes may have the same BrowseName. They are used to build a browse path between two Nodes or to define a standard Property.

Servers may often choose to use the same namespace for the NodeId and the BrowseName. However, if they want to provide a standard Property, its BrowseName shall have the namespace of the standards body although the namespace of the NodeId reflects something else, for example the EngineeringUnits Property. All NodeIds of Nodes not defined in this document shall not use the standard namespaces.

Table 27 provides a list of namespaces that may be used in a Machinery – Process Values OPC UA Server.

Table 28 provides a list of namespaces and their indices used for BrowseNames in this document. The default namespace of this document is not listed since all BrowseNames without prefix use this default namespace.

12 (normative)Machinery – Process Values Namespace and mappings

12.1 NodeSet and Supplementary Files for Machinery – Process Values Information Model

The Machinery - Process Values Information Model is identified by the following URI:

http://opcfoundation.org/UA/Machinery/ProcessValues/

Documentation for the NamespaceUri can be found here.

The NodeSet associated with this version of specification can be found here:

https://reference.opcfoundation.org/nodesets/?u=http://opcfoundation.org/UA/Machinery/ProcessValues/&v=1.00.0&i=1

The NodeSet associated with the latest version of the specification can be found here:

https://reference.opcfoundation.org/nodesets/?u=http://opcfoundation.org/UA/Machinery/ProcessValues/&i=1

The supplementary files associated with this version of specification can be found here:

https://reference.opcfoundation.org/nodesets/?u=http://opcfoundation.org/UA/Machinery/ProcessValues/&v=1.00.0&i=2

The supplementary files associated with the latest version of the specification can be found here:

https://reference.opcfoundation.org/nodesets/?u=http://opcfoundation.org/UA/Machinery/ProcessValues/&i=2

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13 (informative)Examples for Process Values

13.1 Overview

The following table provides two process values and an example of their data associated with it. Note that for the DeviationAlarm, most of the optional Nodes are not shown, and for the LimitAlarm, also most of the mandatory nodes are hidden. They are set similar to the DeviationAlarm.

¹ The PercentageValue in the example is not calculated based on EURange but by some internal logic, also considering other parameters.

² The EURange is from -20 to 180°C, -20 is 0% and +180 is 100%. The absolute deviation value based on a percentage value is “absolute_deviation_value = percentage_value * (max_value – min_value)”. For example, for +5% it is: absolute_deviation_value = 5/100 * 180°C-(-20°C) = 5/100 * 200°C = 10°C.

³ When calculating the absolute limits, in addition to calculating the absolute_deviation_value, it needs to be set into the context of the range, i.e. absolute_value = min_value + absolute_deviation_value. For example, for +5% it is absolute_value = -20°C +10°C = -10°C.

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