Properties of OPC Classic Item Tags

The OPC Item tags, which represent VTScada tags, may reveal the following standard properties. Items that do not have a property name are not available to the VTScada OPC Classic Client.

Property ID	Description	Property name
1	Data Type	N/A
2	Item Value	N/A
3	Item Quality	N/A
4	Item Timestamp	N/A
5	Item access rights (e.g. R/W)	N/A
6	Server scan rate (ms)	N/A
100	EU Units	EUUnits
101	Description	ItemDescription
102	High EU	HighEU
103	Low EU	LowEU
104	High Instrument Range	HighInstrumentRange
105	Low Instrument Range	LowInstrumentRange
106	Contact Close Label	ContactCloseLabel
107	Contact Open Label	ContactOpenLabel
108	Item Timezone	ItemTimezone

The following custom OPC properties have been added to the VTScada tag OPC Items as needed:

ID	Description	Property Name
5000	Area	Area
5001	Device Tag	DeviceTag
5002	Address	Address
5003	Raw (unscaled) Value	RawValue
5004	Low Alarm Limit	LowAlarmLimit
5005	High Alarm Limit	HighAlarmLimit

To access a particular OPC Property value, use the following syntax:

AppOneOPCServer\tags\all\TagName\PropertyName

To access a tag's value, use the syntax:

AppOneOPCServer\tags\all\TagName

Not every tag has all of the properties that are listed in the above tables. The following will help you find whether a property is available for the tag you are interested in.

Property	Available in...
ItemDescription	All tags
EUUnits	All tags with a Units variable
HighEU, LowEU, HighInstrumentRange, LowInstrumentRange	All scalable tags (AnalogStatus, AnalogInput, AnalogControl, AnalogOutput)
ContactCloseLabel, ContactOpenLabel	DigitalStatus
DeviceTag, Address	All I/O tags
RawValue	AnalogStatus and AnalogInput
LowAlarmLimit, HighAlarmLimit	AnalogStatus