Plotting Live and Historical Data
Live data can be plotted for any basic I/O tag (e.g. Analog Input or Digital Input). If you wish to plot historical data for a tag, you must first attach a logger to that tag in order to store the data (*).
The distinction between live and historical plots lies in the time period being displayed. If the time period for the graph is set to the present, then live data is plotted as it is read from the equipment processes in your system. If the time period for the graph is set to the past, then historical data that has been logged or recorded to disk is plotted.
The time slider at the bottom of the Historical Data Viewer will tell you at a glance which type of data you are looking at. While you are viewing live data, the pause button at the right of the slider will look like any other button. While you are viewing historical data, the button will be an arrow surrounded by a red border.
The times shown at either end of the slider are those for the minimum and maximum range of the current live display. They will not change when you switch to a historical view.
For further information, please see:
HDV Time Scale and Date/Time Scroll Bar
(*) Certain tags such as the Analog Status and Digital Status have loggers built in. Never attach a logger tag to an I/O that includes its own logger.
Instructions for the configuration of logger tags is provided in Logger Tags.