dOPC Client Toolkit Help file
TdOPCItemProperty.Id Property
C++
public: __property int Id;
C#
public int Id;
Visual Basic
Public Property Id() As Integer

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 
VT_I2 
"Item Canonical DataType" (VARTYPE stored in an I2) 
OPC_PROP_VALUE 
<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 
VT_I2 
"Item Quality" (OPCQUALITY stored in an I2). This will behave like a read from DEVICE. 
OPC_PROP_time 
VT_DATE 
"Item Timestamp" (will be converted from FILETIME). This will behave like a read from DEVICE. 
OPC_PROP_RIGHTS 
VT_I4 
"Item Access Rights" (OPCACCESSRIGHTS stored in an I4) 
OPC_PROP_SCANRATE 
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. 
 
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. 
 
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 
 
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" 
 
313-399 
 
Reserved for future OPC Alarms and Events use. Additional ID's may be added without revising the interface ID. 
 
400-4999 
 
Reserved for future OPC use. Additional ID's may be added without revising the interface ID. 
 
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.
 
What do you think about this topic? Send feedback!
Copyright © 2001-2014 Kassl GmbH (http://www.kassl.de). All rights reserved.