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Data extension configuration: ExtOpcDa

Description:
Data extension configuration ExtOpcDa - An extension for connecting to the OPC DA communication.
Configuration items:
Data extension identifierSystem text (without spaces and diacritics). It is used for unambiguous identification of data extension in data item (e.g. in the Extension method).

The default value is "opcc".

Target object (PmaOpcDaClientGroup)Path to the target object of appropriate type, in which the data item must be registered. The object can also be selected by the button on the right.By this selection the OPC server, refresh rate and other parameters defined in the PmaOpcDaClientGroup object can be defined.

Macro expression can be used for input, the result must be a NON-LOCALIZED path to Pma object (it is evaluated after starting the application).

ItemIDText address/identifier of the variable in the OPC server. The address can be entered either manually or it can be selected from the window "Viewing the OPC server address space" that can be opened by the button right from the input. But the selective window can be opened only if the OPC-DA server is installed and if it supports the selection.

This configurator sets the initial value of the ItemId property.

Macro expression can be used for input (it is evaluated after starting the application).

AccessPathAccess path to the variable in the OPC server. The value can often be empty. The path can be entered either manually or it can be selected from the selective window that can be opened by the button right from the input. But the selective window can be opened only if the OPC-DA server is installed and if it supports the selection.

This configurator sets the initial value of the AccessPath property.

Macro expression can be used for input (it is evaluated after starting the application).

Value recalculationIf checked, then the received and sent value will be recalculated by the PmValue = k/d * CommValue + q formula, where PmValue is the value in the PROMOTIC system, CommValue is the value from the communication, k,d,q are the recalculation constants defined in the configurator.

The conversion is applied also when sending the value. Then the inversion conversion is done according to the expression CommValue = d/k * (PmValue - q).

Caution: Vhen sending the value with conversion, some inaccuracy may happen and so the PmValue sent could differ from the PmValue received. For example for the conversion of PmValue = 1000 * CommValue and if CommValue is the value on 1B (Range 0-255), then when sending the PmValue=2008 the CommValue=2 is sent. If the CommValue=2 is received, then the PmValue will be 2000.

Macro expression can be used for input (it is evaluated after starting the application).

Note:
This data extension registrates itself automatically into the PmaOpcDaClientGroup object after starting the application. Therefore it is not needed to create the requested item on the "PmaOpcDaClientGroup > Data" tab! If all items for the PmaOpcDaClientGroup object are of the "Data extension" type, then the "PmaOpcDaClientGroup > Data" tab may remain empty.
See also:
- ExtDdeClient (object)
- ExtOpcDa.RecalcK (property)
- ExtOpcDa.RecalcD (property)
- ExtOpcDa.RecalcQ (property)

History:
Pm9.00.10: The Macro expression can now be used for entering the values of recalculating constants k,d,q.
Pm8.03.00: Created
PROMOTIC 9.0.13 SCADA system documentation - MICROSYS, spol. s r.o.

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