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Time range of Graph Measurement

Nov 16, 2015 at 6:49 PM
I recently have a problem. I have two PDCs (two PCs and each of them has openPDC) and one PMU. PMU sends data to PDC1 and PDC1 sends them to PDC2, but the time ranges (x-axis) of Graph Measurement are different. It means that PDC1 Graph Measurement shows the data during 2 seconds while PDC2 shows the data during 30 seconds. I cannot find any display setting to change time range (x-axis). Should I change it when I set the concentration output stream? If so, which parameter is related to the time range?

Nov 16, 2015 at 7:20 PM
Hi liyinbest990,

This was mentioned once in the following discussion, but it's a long discussion so I will copy the relevant portion here.
What you may be noticing with the openPDC Manager is the difference between the "Chart Refresh" of the Manager and the sample rate of the PMUs sending you data. By default, the chart refresh is set to 250 milliseconds. As compared to the updates from the PMU which arrive every 33 milliseconds, it would mean that the Manager is only displaying one data point for every 7 or 8 data points it receives. It would be difficult to synchronize two Managers to show the exact same timestamps at that resolution.

On the Graph Measurements screen, there is a link towards the top just above the graph that says "Display Settings". If you click on that, one of the fields on the left side of the settings window is "Chart Refresh Interval (in miliseconds)". With a good enough graphics card, if you set that to 33, you should be able to see the full resolution of PMU timestamps flying by in that "Time Tag" column. Note that there will be some difference in latency between PDC-1 and PDC-2 that may affect how well synchronized the two systems are, but they should be pretty close.
Nov 16, 2015 at 7:30 PM
I just realized what you were asking about. Using the same "Display Settings" link, the range of the x-axis would be defined by the "Number of Data Points to Plot" field. For example, if I had a PMU recording 30 frames per second, setting that value to 150 would give me 5 seconds of data. Assuming your PMU is also 30 fps, one of your PDCs must have that set to 60 and the other at 900.