Options on the General tab

The following table shows the options on the
General
tab.
Options
Descriptions
Display chart title
Select the check box, and type up to 80 characters in the box provided. The title includes your text and the current date.
The chart title shows at the top of the chart at runtime.
Data server
Select a server to provide data to the trend.
  • None -
    Retrieves data from another source using the Trend object model.
  • Real-time data server -
    Retrieves data from the snapshot subsystem. This option is preferred for points that change infrequently like setpoints.
  • Poll historical data -
    Retrieves data from the archive files. This option is preferred for points that change faster than a second. When using historical polling, the Current Value legend does not show pen icons, or pen values.
    When using
    Poll historical data
     mode, the refresh rate controls how often the data server polls for data. The refresh rate cannot be set to a value lower than one second.
Display progress bar while loading historical data
Select this check box to show progress bar with a
Cancel
button while loading data into the trend. This option allows operators to cancel a request for data at runtime.
Chart style
Determines the plotting style of the chart. A trend chart can plot values against time, or against a selected pen.
Standard
Each pen is plotted against time in a standard line chart.
XY plot
Each pen is plotted against a selected pen, which serves as the x-axis.
To use the option, add a pen under the
Pens
tab, click
Apply
, and then select the pen from the
X-Axis pen
 list.
X-Axis pen
Serves as the x-axis in an XY plot.
Chart update mode
Select one of these options:
  • Manual
  • Automatic
  • On Change
Manual
This option is only available when the
Data Server
 is set to
None
. It does not apply when using the
Real-time data server
, or
Poll historical data
.
In
Manual
mode, the data server sends data to the chart using the NewData method (part of the Trend object model). The NewData method can send accumulated batches of data to the trend in bursts, allowing points to be logged more frequently than once every 50 milliseconds. The data server manages the chart timing, maintains control over the timestamps, and sends the trend an array with new data for each point at the intervals specified in the NewData method. The intervals indicate the spacing of the data in the array.
Automatic
Use this chart mode when you want the trend to update at regular time intervals.
Refresh Rate
In
Automatic
mode, the
Refresh Rate
 specifies how often the chart acquires data. The refresh rate limits are 50 milliseconds to 596 hours. Do not make the refresh rate faster than the rate at which data is updated in the data server, or OPC server.
On Change
Use this chart mode when you want the trend object to update as data values change. In
On Change
 mode, current data updates in the trend chart immediately, as the values change. Specify
On Change
 mode when working with data that changes infrequently. Set the trigger for updates using either a heartbeat rate, or a deadband percentage.
This option is not available when the
Data Server
 is set to
Poll historical data
.
Heartbeat
Specifies the maximum amount of time between updates. If the value of a pen has not changed within the amount of time specified, the chart shows the current value.
Setting the heartbeat rate to 0 disables the heartbeat.
Deadband
Specifies a percentage, by which a value must change before the chart shows the next value.
Setting the deadband rate to 0 updates the chart whenever the value changes.
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