OPC Items can make available supplementary information about themselves: OPC Properties.
The OPC Item tags that represent VTS tags support the following standard properties, where appropriate. Items that do not have a property name are not available to the VTS OPC 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 VTS tag OPC Items, again where appropriate:
|
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, you should use the syntax:
AppOneOPCServer\tags\all\TagName
Not every tag has all of the properties listed in the above tables. The following table will help you determine whether a property is available for the tag you are interested in.
|
Property |
Tags |
|
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 |