In order to display the value changing on the screen in real time, it is necessay that the screen is updated frequently enough, the Trend server is recording enough data points, and that the IOserver is being updating from the device quickly enough.

Using the process analyst the data and screen refresh rates are set in the runtime properties dialog box.  If you chose to use the traditional trend page objects It is necesaary to set the page scan rate in the graphics builder.

When the trend tag is configured in the Project editor it is possible to set the sample period of the trend tag.  To show realtime data it is necessary that the sample period be as fast or faster than the screen refresh rate.

The IOserver needs to have up to date data for the trend server for fast trends.  In the case of version 7.0 which was used in testing for this KB the IOdevice setting for Cache needed to be set to TRUE and the Cache time needed to be set to less than the trend polling rate.  Setting the cache switch to FALSE did not disable the default 300ms cache.

Settings in the IODevice's configeration need to be adjusted so that the data can be retrieved from the device quickly enough.  In the tested case of a local OPC server the address field in the OPC board needed to be set to the device scan rate. Other devices may require adjustments to their citect.ini parameters (particularly the ScanRate parameter if applicable. On the contrary, the PollTime ini parameter should not be modified - read KB Q4915 for more information) , please review the documentation for the protocol you are using.

The maximum number of sample points and screen refresh rates will be entirely depended on the loading and speed of your hardware.