dOPC Client Toolkit
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Id is returned by QueryAvailableProperties or is a fixed value.
The server will need to assign ID codes to these properties. This allows the client to manage the list of properties it wants to access more easily. These properties are divided into 3 sets. The fixed set contains properties that are identical to some of those returned by OPCITEMATTRIBUTES, the recommended set is expected to be common to many servers and the vendor specific set contains additional properties as appropriate. The assigned ID codes for the first two sets are fixed. The vendor specific properties should use ID codes above 5000.
Id |
Data type |
Description | |
OPC_PROP_CDT |
1 |
VT_I2 |
"Item Canonical DataType" (VARTYPE stored in an I2) |
OPC_PROP_VALUE |
2 |
<varies> |
"Item Value" (VARIANT). Note the type of value returned is as indicated by the "Item Canonical DataType" above and depends on the item. This will behave like a read from DEVICE. |
OPC_PROP_QUALITY |
3 |
VT_I2 |
"Item Quality" (OPCQUALITY stored in an I2). This will behave like a read from DEVICE. |
OPC_PROP_time |
4 |
VT_DATE |
"Item Timestamp" (will be converted from FILETIME). This will behave like a read from DEVICE. |
OPC_PROP_RIGHTS |
5 |
VT_I4 |
"Item Access Rights" (OPCACCESSRIGHTS stored in an I4) |
OPC_PROP_SCANRATE |
6 |
VT_R4 |
"Server Scan Rate" in Milliseconds. This represents the fastest rate at which the server could obtain data from the underlying data source. The nature of this source is not defined but is typically a DCS system, a SCADA system, a PLC via a COMM port or network, a Device Network, etc. This value generally represents the best case fastest RequestedUpdateRate which could be used if this item were added to an OPCGroup. The accuracy of this value (the ability of the server to attain best case performance) can be greatly affected by system load and other factors. |
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7-99 |
|
Reserved for future OPC use |
OPC_PROP_UNIT |
100 |
VT_BSTR |
"EU Units" e.g. DEGC or GALLONS |
OPC_PROP_DESC |
101 |
VT_BSTR |
"Item Description" e.g. Evaporator 6 Coolant Temp |
OPC_PROP_HIEU |
102 |
VT_R8 |
"High EU" Present only for analog data. This represents the highest value likely to be obtained in normal operation and is intended for such use as automatically scaling a bargraph display. e.g. 1400.0 |
OPC_PROP_LOEU |
103 |
VT_R8 |
"Low EU" Present only for analog data. This represents the lowest value likely to be obtained in normal operation and is intended for such use as automatically scaling a bargraph display. e.g. -200.0 |
OPC_PROP_HIRANGE |
104 |
VT_R8 |
"High Instrument Range" Present only for analog data. This represents the highest value that can be returned by the instrument. e.g. 9999.9 |
OPC_PROP_LORANGE |
105 |
VT_R8 |
"Low Instrument Range" Present only for analog data. This represents the lowest value that can be returned by the instrument. e.g. -9999.9 |
OPC_PROP_CLOSE |
106 |
VT_BSTR |
"Contact Close Label" Present only for discrete' data. This represents a string to be associated with this contact when it is in the closed (non-zero) state e.g. "RUN", "CLOSE", "ENABLE", "SAFE",etc. |
OPC_PROP_OPEN |
107 |
VT_BSTR |
"Contact Open Label" Present only for discrete' data. This represents a string to be associated with this contact when it is in the open (zero) state e.g. "STOP", "OPEN", "DISABLE", "UNSAFE", etc. |
OPC_PROP_TIMEZONE |
108 |
VT_I4 |
"Item Timezone" The difference in minutes between the items UTC Timestamp and the local time in which the item value was obtained. See the OPCGroup TimeBias property. Also see the WIN32 TIME_ZONE_INFORMATION structure. |
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109-199 |
|
Reserved for future OPC use. Additional IDs may be added without revising the interface ID. |
OPC_PROP_DSP |
200 |
VT_BSTR |
"Default Display" The name of an operator display associated with this ItemID. |
OPC_PROP_FGC |
201 |
VT_I4 |
"Current Foreground Color" The COLORREF in which the item should be displayed. |
OPC_PROP_BGC |
202 |
VT_I4 |
"Current Background Color" The COLORREF in which the item should be displayed. |
OPC_PROP_BLINK |
203 |
VT_BOOL |
"Current Blink" Should a display of this item blink? |
OPC_PROP_BMP |
204 |
VT_BSTR |
"BMP File" e.g. C:\MEDIA\FIC101.BMP |
OPC_PROP_SND |
205 |
VT_BSTR |
"Sound File" e.g. C:\MEDIA\FIC101.WAV, or .MID |
OPC_PROP_HTML |
206 |
VT_BSTR |
"HTML File" e.g. http:\\mypage.com/FIC101.HML |
OPC_PROP_AVI |
207 |
VT_BSTR |
"AVI File" e.g. C:\MEDIA\FIC101.AVI |
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208-299 |
|
Reserved for future OPC use. Additional IDs may be added without revising the interface ID. |
OPC_PROP_ALMSTAT |
300 |
VT_BSTR |
"Condition Status" The current alarm or condition status associated with the Item e.g. "NORMAL", "ACTIVE", "HI ALARM", etc. |
OPC_PROP_ALMHELP |
301 |
VT_BSTR |
"Alarm Quick Help" A short text string providing a brief set of instructions for the operator to follow when this alarm occurs. |
OPC_PROP_ALMAREAS |
302 |
VT_BSTR |
"Alarm Area List" An array of stings indicating the plant or alarm areas which include this ItemID. |
OPC_PROP_ALMPRIMARYAREA |
303 |
VT_BSTR |
"Primary Alarm Area" A string indicating the primary plant or alarm area including this ItemID. |
OPC_PROP_ALMCONDITION |
304 |
VT_BSTR |
"Condition Logic" An arbitrary string describing the test being performed. e.g. "High Limit Exceeded" or "TAG.PV >= TAG.HILIM" |
OPC_PROP_ALMLIMIT |
305 |
VT_BSTR |
"Limit Exceeded" For multistate alarms, the condition exceeded e.g. HIHI, HI, LO, LOLO |
OPC_PROP_ALMDB |
306 |
VT_R8 |
"Deadband" |
OPC_PROP_ALMHH |
307 |
VT_R8 |
"HiHi Limit" |
OPC_PROP_ALMH |
308 |
VT_R8 |
"Hi Limit" |
OPC_PROP_ALML |
309 |
VT_R8 |
"Lo Limit" |
OPC_PROP_ALMLL |
310 |
VT_R8 |
"LoLo Limit" |
OPC_PROP_ALMROC |
311 |
VT_R8 |
"Rate of Change Limit" |
OPC_PROP_ALMDEV |
312 |
VT_R8 |
"Deviation Limit" |
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313-399 |
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Reserved for future OPC Alarms and Events use. Additional ID's may be added without revising the interface ID. |
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400-4999 |
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Reserved for future OPC use. Additional ID's may be added without revising the interface ID. |
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5000-... |
VT_xxx |
Vendor Specific Properties. ID codes for these properties must have values of 5000 or greater. They do not need to be sequential. The data types must be compatible with the VARIANT. |
TdOPCDAClient.GetItemProperty
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