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5.1.1 OPC Recommended Properties


   In OPC there is a recommendation of what properties are expected to be supported by an alarm & event server. The recommended properties are shown in Table 5-1. The column names correspond to the attributes in the Property class.

   Table 5-1 Recommended Properties Table 5-1 Recommended Properties

label

id

canonical_ data_type

description

Condition Status 300 STRING_TYPE The current alarm or condition status associated with the Item (for example, “NORMAL,? “ACTIVE,? “HI ALARM?).
Alarm Quick Help 301 STRING_TYPE A short text string providing a brief set of instructions for the operator to follow when this alarm occurs.
Alarm Area List 302 STRING_TYPE sequence An array of strings indicating the plant or alarm areas that include this ItemID.
Primary Alarm Area 303 STRING_TYPE A string indicating the primary plant or alarm area including this ItemID.
Condition Logic 304 STRING_TYPE An arbitrary string describing the test being performed (for example, “High Limit Exceeded? or “TAG.PV >= TAG.HILIM?). Refer to Section 5.2.7.3, “Condition Logic,? on page 5-38.

Limit Exceeded

Deadband

HiHi Limit

Hi Limit

Lo Limit

LoLo Limit

Rate of Change Limit

Deviation Limit

305 STRING_TYPE For multistate alarms, the condition exceeded (for example, HIHI, HI, LO, LOLO).
306 DOUBLE_TYPE Deadband
307 DOUBLE_TYPE HiHi Limit
308 DOUBLE_TYPE Hi Limit
309 DOUBLE_TYPE Lo Limit
310 DOUBLE_TYPE LoLo Limit
311 DOUBLE_TYPE Rate of Change Limit
312 DOUBLE_TYPE Deviation Limit
3124999 Reserved by OPC