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For every OPC Item that you connect the OPC Time Monitor to in one of your OPC
Servers, the OPC Time Monitor will calculate and expose a set of tags upstream to any OPC client that is interested. The items exposed are grouped into a hierarchy
that your client application can browse using OPC Item browsing, so you do not have to remember the different pieces of information that are available.
- Basic Tags - summary and control tags - the first ones seen for any given
OPC item - see below
- Condition Summary Tags (Supplied separately for "In-Condition", "Out-of-Condition", and "Stable" states
- Condition Aggregate Tags (Supplied separately for "In-Condition",
"Out-of-Condition", and "Stable" states
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 Basic Tags
These tags appear when you browse the OPC Time Monitor and first select an Item as shown at the right.
These 5 tags provide basic information about the current state of the tag relative to the compliance conditions you have configured and provide a tag for resetting the current aggregates.
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Name
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Access Rights
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Canonical (Default) Data Type
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Description
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Readable
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Writeable
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$CurrentValue
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Yes
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No
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VT_EMPTY *
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Passed-through current value of the measured (source) item.
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$InCondition
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Yes
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No
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VT_BOOL
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True of the configured "conditions" for this OPC item in the OPC Time Monitor have been met.
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$OutOfCondition
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Yes
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No
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VT_BOOL
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True of the configured "conditions" for this OPC item in the OPC Time Monitor have NOT been met. Value should typically be the
opposite of $InCondition.
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$Reset
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Yes
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Yes
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VT_BOOL
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Writing True value into this item resets the aggregates under this level and below. Reading this item always returns False in this
version.
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$Stable
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Yes
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No
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VT_BOOL
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True of the configured stability condition for this OPC item in the OPC Time Monitor has been met, false otherwise.
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* Note: The server reports VT_EMPTY as a canonical data type for CurrentValue and PreviousValue items. This is a
common OPC way to express that the canonical data type of a value is unknown at the moment. The actual values returned
by the OPC Time Monitor server have the same data type as the underlying server that provides them. Some OPC Client
applications require that the OPC server present a data type. For that reason, the OPC Time Monitor allows you to set force a data type for each item instead of presenting VT_EMPTY.
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