Traces
The trend chart updates every second. Updates occur even if there is no sample data to display for the current time span. The time span is the length of time shown on the trend chart.
Each trend chart can display data for up to eight traces. Samples, or data values at specific points in time captured at the specified rate, are plotted on the trend chart in the specified time span. Traces automatically display data from a data log for the specified tag. Samples connect to create a linear trace. If there are multiple traces and one or more traces are in error, the traces that are in error are not plotted on the trend chart. Traces that are not in error plot data on the trend chart.
For each trace on a trend chart, samples are plotted using a horizontal axis representing time and a vertical axis representing the value. By default, labels appear on each axis. The time axis shows placeholder labels for time and the y-axis shows labels based on the minimum value and maximum value of the trend chart.
View Designer
does not support configuring these labels.
TIP:
Tips:
- If data is not available for a specific time period, the trend chart displays a gap in the trace. For example, the HMI device may temporarily lose connection with a controller.
- For applications already downloaded to the HMI device, it may take up to the length of the sample rate before data shows on the trend chart. For example, if the trend chart has a sample rate of 30000 milliseconds or 30 seconds, it may take up to 30 seconds before any data shows on the trend chart. In some cases, it can take twice the sample rate before data shows on the trend chart. For example, if the sample rate is one minute and the application is just being downloaded to the HMI device and communication to a controller is being established, it may take an additional minute to plot data. No trace appears until there are two data points to plot.
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