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[KB70]Deadbands with Schneider OFS

Tags: OPC, OPC-DA Server, PlantVue

Communication interfaces
14 years ago
By RM
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Applies to:

PcVue all versions.
PlantVue all versions.
Summary:

This article describes how to configure the deadbands of Schneider’s Office Factory Server (OFS).
Details:

Deadbands with OFS

Correct management of the deadbands used in the OFS is essential. The deadband configuration is accessed by switching the OFS Configurator to advanced mode using the Advanced button in the Alias tab.

DeadbandsWithOFS_Config_Deadband_tab_PcVuePV_Fr

The deadbands used by the OFS are an absolute value calculated according to a configured range and the deadband of the group of the OPC client. The following formula is used.

Deadband = x%*(Max – Min)

  • x% is the deadband of the group referenced by the OPC client.
  • Max and Min are the values you will have entered in the Value Min and Value Max fields.

Depending on the configuration of the variables it may therefore be necessary to configure a number of deadband types and a number of OPC groups (with different deadbands).

PcVue and OFS

Consider the following configuration in the OFS.

DeadbandsWithOFS_Config_Deadband_tab_varslist_PcVuePV_Fr

Configuring the deadband of the OPC group of PcVue

The OPC group’s deadband, as configured in the Advanced tab, is expressed as a percentage (0 to 100) for transmission to the OPC client. The OFS however expects a value in the range 0 to 1 and since there is no conversion you must ignore the fact that it is supposed to be a percentage and enter a value between 0 and 1 instead.

DeadbandsWith3

Declaring the variables

When you define a OFS OPC server variable in PcVue you must append the name of the deadband to be used to the item name. For example, PREMIUM! % MF600@.

DeadbandsWithOFS_VarConfig_dlg_PcVue_Fr

Assuming a deadband of 0.01 in the OPC group:

  • The value of the variable with an item name of PREMIUM! % MF600@DEADBANDTYPE1 would be notified when it changes by 1 or more.
  • The value of the variable with an item name of PREMIUM! % MF600@DEADBANDTYPE2 would be notified when it changes by 0.01 or more.

PlantVue and OFS

Consider the following configuration in the OFS.

DeadbandsWithOFS_Config_Deadband_tab_varslist_PcVuePV_Fr

Configuring the deadband of the OPC group in PlantVue

When using PlantVue you have the option of expressing the deadband as either 0 to 1 or 0 to 100%. This is selected in the OPC server configuration. For the OFS you must select the 0 to 1 option.

DeadbandsWithOFS_Config_OFSnode_PV_Fr

Configuration in the trend group

In the trend group, you must express the deadband as a percentage (0 to 100). This is then automatically converted to the 0 to 1 range expected by the OFS.

That is the value that is automatically converted, or not, according to the deadband interval setting as above.

Declaring the variables

When you define a OFS OPC server variable in Plantue you must append the name of the deadband to be used to the item name. For example, PREMIUM! % MF600@

DeadbandsWithOFS_Config_PremiumMF600node_PV_Fr

Assuming a deadband of 5 in the Trend Group (equivalent to 0.05 in the OFS):

  • The value of the variable with an item name of PREMIUM! % MF600@DEADBANDTYPE1 would be notified when it changes by 5 or more.
  • The value of the variable with an item name of PREMIUM! % MF600@DEADBANDTYPE2 would be notified when it changes by 0.05 or more.

Differences between historic and real time processing

If you implement a test display of this variable in a trend curve, the shape of that curve does not necessarily reflect recording to an archive since it may well be updated by another OPC group called Real Time.

Created on: 15 Oct 2010 Last update: 13 May 2024