Opc data Access Automation Specification

4.6.3.14

 

EUInfo  

Description 

(Read-only) Variant that contains the Engineering Units information 

Syntax 

 EUInfo As Variant 

See Also 

OPCITEMATTRIBUTES in the OPC Data Access Custom Interface Specification 

Example 

Dim AnOPCItem as OPCItem 

Set OPCItem = GetOPCItem(SomeItemServerHandle) 

VB Syntax Example (getting the property): 

Dim CurrentValue As Variant 

Dim SomeValue As Variant 

CurrentValue = AnOPCItem.EUInfo 

4.6.4

 

OPCItem Methods 

4.6.4.1

 

Read 

Description 

Read makes a blocking call to read this item from the server. 

Read can be called with only a source (either OPCCache or OPCDevice) to refresh the item’s 

value, quality and timestamp properties. If the value, quality and timestamp must be in sync, this 

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OPC Data Access Automation Specification2.02 

method’s optional parameters return values that were acquired together. 

Syntax 

 Read (Source As Integer, Optional ByRef Value As Variant, Optional ByRef Quality As Variant, 

Optional ByRef TimeStamp As Variant) 

 

Part Description 

Source 

The ‘data source’; OPC_DS_CACHE or OPC_DS_DEVICE  

Value 

Returns the latest value read from the server 

Quality 

Returns the latest value read from the server 

TimeStamp 

Returns the latest timestamp read from the server. 

 

Example 

Private Sub ReadButton_Click() 

Dim AnOPCItem as OPCItem 

Set OPCItem = GetOPCItem(SomeItemServerHandle) 

Dim Source As Integer 

Dim Value As Variant  

Dim Quality As Variant  

Dim TimeStamp As Variant 

Source = OPC_DS_DEVICE 

AnOPCItem.Read Source, ServerHandles, Value, Quality, TimeStamp 

 ‘ process the values 

TextBox.Text = Value 

End Sub