Item type: Function item
This Item is a calculated value based on existing items in Hive. The calculation is formula based on inputs from external Items.
This item has two different calculators (algorithm syntax), C# and Legacy (proprietary), see:
The Function item item type has the following properties:
| Name | Description | ID | Flags |
|---|---|---|---|
| Expression | An expression used to calculate the value of this item | 5110 | Persisted |
| Expressions | Definitions of array inputs to the calculator (applicable for C# only) | 5111 | Persisted |
| Calculator | Specifies which calculator to use, C# or legacy | 19101 | Persisted |
| DataChangeTrigger | The DataChangeTrigger is an enumeration that specifies the conditions for when the Function item should be reported as updated inside APIS after a calculation. Quality: Report as updated only if the Qualtiy associated with the value changes. QualityValue: Report as updated if either the Qualtiy or the Value change. QualityValueTimestamp: Report as updated if either Quality, Value or the Timestamp change (default). | 19102 | Persisted, Enumerated |
| External Items | The external items that are inputs to the formula given by the Expression property | 20000 ... 20000+N | Persisted |
| Quality | Item quality | 3 | NormalPage |
| Rights | Item access rights | 5 | ReadOnly |
| Time | Item timestamp | 4 | NormalPage |
| Type | Item canonical datatype | 1 | ReadOnly |
| Value | Item value | 2 | NormalPage |
| Valuetype | Item canonical datatype. | 19100 | Persisted, Enumerated |
See also Predefined Item Properties and OPC DA Properties