The ProcessItemType is used to measure and monitor over time a measurement point. The ProcessItemType also provides aggregates (Avg, Max, Min, Std, Total) that are computed by the underlying system. The aggregates are computed over a time period or for a product quantity and can be configured by a client altogether with the sampling time.
The ProcessItemTypeis formally defined in the following table.
Table 129– ProcessItemType Definition
|
Attribute |
Value |
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|
BrowseName |
ProcessItemType |
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|
IsAbstract |
False |
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|
References |
Node Class |
BrowseName |
DataType |
TypeDefinition |
Other |
|
Subtype of the BaseObjectType defined in OPC 10000-5 - Part 5: Information Model, i.e. inheriting the Instance Declarations of that Node. |
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|
0:HasProperty |
Variable |
AggregationWindow |
0:UInt32 |
0:PropertyType |
M, RW |
|
0:HasComponent |
Object |
LimitAlarms |
|
0:NonExclusiveLevelAlarmType |
M |
|
0:HasComponent |
Variable |
Value |
0:Double |
DisplayAnalogUnitType |
M, RO, HR |
|
0:HasComponent |
Variable |
Avg |
0:Double |
0:BaseDataVariableType |
M, RO, HR |
|
0:HasProperty |
Variable |
LastResetTime |
0:UtcTime |
0:PropertyType |
M, RO |
|
0:HasComponent |
Variable |
Max |
0:Double |
0:BaseDataVariableType |
M, RO |
|
0:HasComponent |
Variable |
Min |
0:Double |
0:BaseDataVariableType |
M, RO |
|
0:HasComponent |
Method |
ResetAggregates |
See below. |
M |
|
|
0:HasComponent |
Variable |
SamplingRate |
0:Double |
0:AnalogUnitRangeType |
M, RW |
|
0:HasComponent |
Variable |
Std |
0:Double |
0:BaseDataVariableType |
M, RO, HR |
|
0:HasComponent |
Variable |
Total |
0:Double |
0:BaseDataVariableType |
M, RO |
|
0:HasComponent |
Object |
UIInfo |
|
UIInformationType |
O |
|
0:GeneratesEvent |
ObjectType |
0:NonExclusiveLevelAlarmType |
|
|
|
|
0:GeneratesEvent |
ObjectType |
ProcessItemResetLogType |
|
|
|
|
Conformance Units |
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|
TMC Process Variables Ingestion and Control |
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Each valid ProcessItemcan have one or more PrecedesReferences pointing to other downstream ProcessItems.
The components of the ProcessItemTypeare further described below.
|
BrowseName |
Description |
|
AggregationWindow |
Tthe number of samples over which the aggregates are computed. When the number of aggregated samples since the last reset exceeds the AggregationWindow, the aggregates are rolled over, i.e. computed over the last AggregationWindow number of samples. The value of the AggregationWindowcan be set by a client to obtain the desired aggregation. If the written value is below (above) the minimum (maximum) value that can be managed by the underlying system, the underlying system will overwrite it with the minimum (maximum). |
|
LimitAlarms |
The deviation alarm with 4 thresholds: HighHigh, High, Low, LowLow. All 4 thresholds shall be supported. |
|
Value |
Value represents the current value measured by the sensor. |
|
Avg |
The average of valid values over the last AggregationWindowsamples and after the last reset. It is only reset by the successful execution of the ResetAggregates method. |
|
LastResetTime |
The time (in UTC) when ResetAggregateswas last successfully executed. |
|
Max |
The maximum valid value for the last AggregationWindowsamples and after the last reset. It is only reset by the successful execution of the ResetAggregatesmethod. |
|
Min |
The minimum valid value for the last AggregationWindowsamples and after the last reset. It is only reset by the successful execution of the ResetAggregatesmethod. |
|
SamplingRate |
The rate samples are collected for aggregation. The rate is referred to the either product or time, as indicated by the EURangeproperty. For example, SamplingRateequal to 100 ms means that the value is measured and collected for aggregation every 100 ms. SamplingRateequal to 10 kg means that the value is measured and collected for aggregation every 10 kg of product. SamplingRateequal to 100 rods means that the value is measured and collected for aggregation every 100 rods of product. The EURangeproperty of the SamplingRateis read only and defines both the unit of measure and the supported range. The value of the SamplingRatecan be set by a client to obtain the desired sampling rate for aggregation. If the written value is below (above) the minimum (maximum) value that can be managed by the underlying system, the underlying system will overwrite it with the minimum (maximum). The underlying system will support equivalent sampling rates of 100ms or better. |
|
Std |
The standard deviation of the valid value for the last AggregationWindowsamples and after the last reset. After reset, when only one value is available, the standard deviation is not defined and zero will be returned. It is only reset by the successful execution of the ResetAggregatesmethod. |
|
Total |
The accumulated total of the valid value for the last AggregationWindowsamples and after the last reset. It is only reset by the successful execution of the ResetAggregatesmethod. |
|
UIInfo |
The visualization resources to display the ProcessItemTypeon the UserInterface. |
The ResetAggregates Method restarts from new the computation of aggregates performed by the underlying system.
The signature of this Methodis specified below. Table 130specifies the Argumentsrepresentation.
Signature
ResetAggregates (
[out] MethodExecutionFeedbackType ExecutionFeedback);
Table 130– ResetAggregates Method Arguments
|
Argument |
Description |
|
ExecutionFeedback |
The extended feedback returning a detailed message in case of execution failure. |
When the ResetAggregatesmethod is invoked, an event of type ProcessItemResetLogTypeis generated with the last value of the aggregate variables, then the aggregates are reset as specified and the LastResetTimeis set at the time when the method completes successfully.