The JoiningDataVariableType is a subtype of the BaseDataVariableType. It is to describe common sematic required for variables in a given system. In this version of the specification, it provides information about physical quantity and Engineering Units. It is formally defined in Table 67.
Table 67 - JoiningDataVariableType Definition
|ValueRank||−2 (−2 = Any)|
Subtype of the BaseDataVariableType defined in OPC 10000-5.
The optional PhysicalQuantity is to determine the type of the physical quantity associated to a given value(s). It has the following pre-defined values which shall be used for each instance of this type.
- 0 - OTHER
- 1 - TIME
- 2 - TORQUE
- 3 - ANGLE
- 4 - IMPULSE
- 5 - DISTANCE
- 6 - AREA
- 7 - VOLUME
- 8 - FORCE
- 9 - PRESSURE
- 10 - VOLTAGE
- 11 - CURRENT
- 12 - RESISTANCE
- 13 - POWER
- 14 - ENERGY
- 15 - MASS
- 16 - TEMPERATURE
- 17 - FREQUENCY
- 18 - JOLT
- 19 - VIBRATION
- 20 - NUMBER
- 21 - DISTANCE_SPEED is the change of distance over time.
- 22 - ANGULAR_SPEED is the change of angle over time.
- 23 - DISTANCE_ACCELERATION is the change of DISTANCE_SPEED over time.
- 24 - ANGULAR_ACCELERATION is the change of ANGULAR_SPEED over time.
- 25 - TORQUE_SPEED is the change of torque over time.
- 26 - TORQUE_ACCELERATION is change of TORQUE_SPEED over time.
- 27 - TORQUE_PER_ANGLE_GRADIENT is the change of torque over angle.
- 28 - TORQUE_PER_ANGLE_GRADIENT2 is the change of TORQUE_PER_ANGLE_GRADIENT over angle. Example: It is used for yield and snug detection. It represents change of the slope in a torque over angle graph. The optional 0:EngineeringUnits defines the engineering unit of the values.
Note: The quantity and units of the value is of importance and it is going to be defined in harmonized way. This specification waits for this to be solved in the base OPC UA specification (OPC 10000-8), and that will be updated afterwards.
Note on Physical Quantity and Engineering Units
JoiningDataVariableType defined in 9.10 describes a minimal way to provide the PhysicalQuantity and EngineeringUnits properties for a given value.
This might get updated in future version based on the updates from OPC UA Core Specifications. Hence the JoiningDataVariableType properties are marked as Optional to avoid breaking changes later.
An application can ensure that those are available by using a corresponding Conformance Unit defined for this use case.
If an application does not provide the EngineeringUnits for a given value, it is assumed to be in International System of Units (SI).