|
OPC Data Logger Version 3 |
|
Last updated: February 1, 2011 |
The group is a logical place-holder for storing:
Items - the names of the items to log.
Read Method - how the data should be retrieved from the Data Collector.
Triggers - group events that can be called by an external Trigger.
The Group Properties window can be opened by first opening the Project properties window, and then highlighting a Group in the Groups Tab and then choosing the Properties option or by double clicking on the group. You can also open the Group properties by right clicking on the Group name in the tree view and selecting Properties.
Group Name: The name of this group.
Description: (Optional) A simple description of the group.
This tab contains a list of the names of the items to log.
Simple Name: (Optional) A name that can be given to the item that the user determines.
ItemID: The name of the item that you want to log.
Description: (Optional) A description of the item.
Value: (Read Only) The current value of the item. This value will change while data is being logged.
Quality: (Read Only) The current quality status of the item.
Timestamp: (Read Only) The timestamp representing when the current value was updated.
Update Count: (Read Only) The number of updates this item has received.
Previous Value: (Read Only) The previous value of the item.
Previous Quality: (Read Only) The previous quality of the item.
Previous Timestamp: (Read Only) The previous timestamp of the item.
Active: Whether or not the item is active. The Data Logger engine will use this flag to determine if an item should be used for data collection or not.
Last Error Number: (Read Only) The last error number, if exists.
Last Error: (Read Only) Details of the last error, if applicable.
Data Type: (Optional) The data-type of the item. This is automatically set when importing items from your data source.
Deadband: (Optional) The percent change required in the value to receive updates.
Scan Rate: (Read Only) The requested scan-rate that the data source should use when polling this item.
Add Menu
Add new Item: Allows you to manually add an item to the list.
Browse for Items to Add: Opens the Group and Item Browser dialog allowing you to browse the data source to pick the items to add to this list.
Remove menu:
Remove All: Removes all of the items in the list, essentially clearing the list.
Remove Selected: Removes all of the items that have been highlighted. To highlight items you can simply click on an item, or if you click on an item and then hold down the SHIFT key and then press a 2nd item, then those two items and all of the items in-between will be selected as a range.
Import menu:
Import from File menu:
Data Logger (*.csv): Allows you to import items that were previously exported from the OPC Data Logger application.
TOPServer (*.csv): Allows you to import items that were previously exported from the Software Toolbox TOPServer OPC Server.
INGEAR (*.csv): Allows you to import items that were previously exported from an INGEAR OPC Server.
Import directly from Server: This option will try to perform an automatic detection and import of items directly from the data source itself. This option is especially useful when collecting data from OPC Servers or other data sources that allow item browsing.
Export: Allows you to export the list of items that you see within this window to a text file (*.csv).
Refresh menu:
The refresh options will cause the items list to be refreshed, which
can be useful when monitoring the values of the items.
Refresh every 1-second
Refresh every 5-seconds
Refresh every 10-seconds
Stop Auto-Refreshing
Refresh Now
This tab specifies just how the items should be read/collected from the Data Source.
Interval: For Subscription or Timer based reads, the interval on which the updates will occur. Can be specified in msec, sec or min.
Subscription Base Reads: Subscriptions are the preferred method of reading. A subscription works "by exception". This means that the data source will continuously poll the target device/PLC and will notify the application when values change. Because the target device/PLC is always being polled, the data will always be fresh. Also, because the application is receiving the value change event notifications only, it will help with resources and bandwidth between the two systems.
Timer Based Reads: If you absolutely need to control when the device/PLC is read, then you can opt to use a timer. There is no benefit to using a timer over subscriptions, in fact to the contrary, Timer based reads are far less efficient than subscriptions.
Triggered Reads: When you don't need to continuously poll for your data, you can simply use a trigger to initiate one-time-reads from your data source. This can be useful when you wan to accomplish a schedule such as reading an item at 9am, 12pm and 5pm for example, or read an item when another item that is being monitored reaches a particular threshold.
Behavior section: When using Timer or Triggered reads, two further options will be available, one must be selected for use:
Synchronous
Each read will be done synchronously. This means that the connection
the Data Logger makes to the applicable data source will be "blocked"
on each read. Synchronous behavior is the most
reliable but also the most expensive.
Asynchronous
Each read will be done asynchronously. This means that each read
request will be issued to the data collector and the results will be processed
whenever they turn up, as opposed to synchronous which halts operations
until the values arrive. Many data collectors such as OPC Servers optimize
asynchronous calls, but do not optimize synchronous calls. This may mean
that the underlying bandwidth to your device/PLC may be greater and consequently
slower when using synchronous calls.
Triggers can invoke specific behaviors on the group. Please refer to the Triggers section for specific information on the triggers themselves.
In this screen you can add, edit and remove triggers.
"Effects" are the behaviors on a group that can be executed by a trigger:
Resume Group: Enables the group for data collection. During runtime, this will cause items to start being polled by the data collector.
Pause Group: Disables the group for data collection. During runtime, this will cause items that are being polled by the data collector to be temporarily suspended.
One-shot Read Now: Requests the group to perform a one-shot read of all the items within the group now.