Simple_Maintenance (Customer) asked a question.

October 19, 2026 at 6:15 PM
CM5-RHMI Line Chart behavior issue, stops updating

I programmed my CM5-RHMI with software Ver9.02 and I have a line graph object that will build and display a line graph for a while but then it stops updating after a period of time and I think it is caused by surpassing a maximum number of data points. I am unsure if this is the cause or how to fix it. I want the line graph to display new data perpetually / as long as the HMI is on.

 

The Data Source is set to "Live Data Mode" with a sample rate of 2 seconds and total stored points of 43200. The instructions say that the maximum stored points is 65535. I chose 43200 because at 2 second intervals I should be able to show 24 hours of data on the line chart.

 

I do not care about logging the data or being able to scroll back and view data older than 24 hours. My chart seems to work for a few days (or at least longer than 24 hours) and then it just stops updating and leaves the existing graph on the screen.

 

It is my belief that the HMI should gather the 43200 data points and then overwrite the oldest data point with the newest one and in this way be able to continuously display... Am I not understanding this?

 

Thanks

  • 2 answers
  • 65 views

  • K Price (Customer)

    You are correct that the oldest data points should drop off to make room for the newest data points once the number of total stored points is reached. As far as the "stops updating" problem:

    1: Is the Sample Rate fixed at 2 sec? Or does the Sample Rate come from tag of a PLC timer/toggle? Thinking if the PLC timer is stopping due to PLC code?

    2: Could something be happening to PLC-HMI communications? Such that a buffer becomes full? Perhaps an easy way to test this is to set the Sample Rate to 4 seconds, and see if the problem goes away.

    3: Could the memory limits be exceeded? How many Line Charts on the HMI? How many data points on each Line Chart? Can you build a Line Chart with just (1) data point? Did the problem go away?

    4: Can you monitor the HMI memory/resource/error status during the stop of updating? Does the HMI memory/resource/error status windows show any problems?

     

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  • Simple_Maintenance (Customer)

    1. fixed 2 sec.
    2. communication has no issue
    3. Now that you mention it, this probably is the issue. I have 3 line charts building simultaneously off the same data, so I can see 5 minutes, 1 hour, and 24 hours simultaneously. Each graph has 3 pens. So probably the maximum stored points of 65535 is shared among all the graphs and I have been exceeding this. I will lower the sample rate significantly to see if this fixes it, I do not need the hour graph to show at 2 second intervals
    4. I will check this also next time I see the issue.

    Thanks for the ideas.

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