PMUConnectionTester Frequency and Phase Graphs Time Scales Not Synchronized

While watching the graphics display chart in PMUConnectionTester, I noticed that the Frequency and Phase charts do not stay aligned.

At first, I thought this was the number of samples plotted on each chart, so I made sure the sample counts are the same. In the screen shots below each chart is set for 600 points to plot.

Next, I thought maybe the issue was caused by the Phase Angle chart being slightly longer than the Frequency chart. The left side axis lines do not line up. OK, I could see that this might cause the points to be plotted with different spacing.

However, I observe that sometimes the Frequency and Phase graphs stay in line for a little while then other times the Frequency graph advances much quicker than the Phase graph. That is, the rate of the shift changes. I would think that if the cause was simple scaling, the rate of shift would be constant.

I’m not sure if this is a problem that needs to be fixed. This issue would be hard to observe with the default settings. I have not ruled out that my settings for the number of points to plot and absolute phase angle are out of bounds with respect to PMUConnectionTester’s typical use. Since there are no time scales on the graphs - there is probably no reason to expect the graphs to be tightly synchronized. After all, it’s a PMU tester, not a Graphics tester B-)

The following screen shots are about 5 seconds apart. The second screen shot shows that the Phase Angle graph did not “keep up” with the Frequency graph.

PMUConnectionTester version Screen Shots

Phase Angle Graph is now trailing the Frequency Graph by about 5 seconds.

Hi AJ - yeah, I don’t even think the default number of points to plot per graph are even the same and the data being graphed is using lots of multithreading just to get data up and on the screen in a timely manner. It was never really the design intention for this to be a visualization and analysis tool, although many people use it that way because it so simple to use.

We are working now on more portable UI interfaces for our tools, specifically web based HTML5 - we will keep this feature request in mind if we are also able to rewrite the connection tester.


What I like most about PMUConnectionTester are that it assures me that my PMUs properly communicate and the graphics are a nice quick data check.

In this case, PMU Connection Tester is telling me I have a periodic frequency measurement glitch in my PMU !