parenthesis in cursor data

[RavensFan]

Here is something I haven't seen before, and am wondering why it might happen.

I am looking at some data, and am using a multi-plot cursor to look at data on a graph.  Acquisition rate is 10 MHz and I'm zoomed in tight.

The cursor shows data normally.  Then I click over a little bit, and the cursor shows the data, but with parentheses around the values.  Next click, the parentheses are gone.

What does the parenthesis mean?

Interestingly, the value are identical in picture 1 and 2.  Picrtures 2 and 3 have the slight differences that I would expect.  Note that this waveform data was created in another VI and saved to a TDMS file.  I've opened up the TDMS file to display and for further processing here.

I've seen this in other places throughout the data, and now I'm seeing the value being identical.  I'll have to go back and dig into the actual waveform arrays to see if the data in the corresponding points are identical or not.  I'll update the thread once I find out.  I'm going to guess this is some artifact of the waveform graph, perhaps since my dT is so small with the 10 MHz sampling rate.

This is LV 2014 SP1 f3

[Gregory]

Are they free cursors? Could it be there to tell you that you don't actually have a value at that point in time, so it is just taking the amplitudes at the nearest time that does have a point?

[johnsold]

That would be my guess also.  It looks like the cursors in the first two pictures are not at the sampling points.

Lynn

[RavensFan]

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@Gregory wrote:

Are they free cursors? Could it be there to tell you that you don't actually have a value at that point in time, so it is just taking the amplitudes at the nearest time that does have a point?

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No.  They are multi-plot cursors.  All 3 graphs were grabbed after I manipulated the cursors left and right using the little cursor keypad triangles.  Though this is the first time I've played with multi-plot cursors.  I generally work with single plot.

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@johnsold wrote:

That would be my guess also.  It looks like the cursors in the first two pictures are not at the sampling points.

Lynn

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I'm not sure why you think the first two pictures look different, other than the third picture has the cursor points on the major grid line.  The first picture on a minor gridline.  And the 2nd between grid lines.  I don't have markers showing for the data points.  But the dT is 0.000 000 100 , 100 nanoseconds.  Data was downloaded from a oscilloscope acquiring 4 channels at 10 MS/sec on each channel.  So a data point is on every minor gridline, and on a spot between the minor gridlines.

I'm going to attach the VI with just that graph with the data saved as default.  (Zipped up to reduce the size of the VI.  The original was just over 6 MB, too big to upload to the forums.)

I just realized one more thing that might come into play.  When I saved the data to the TDMS, I saved it as a Waveform of Single.  (I wanted to minimize the number of bytes used in the file.)  I used parts of the TDMS Viewer VI to read the data into my analysis program.  I just noticed that it brought it in as a Waveform of Double datatype.  Why that would affect the graph, I have no idea.  But I am now worried that my data is not reading back in correctly.  But from what I can tell the waveform matches with what it looked like before being written to the file, is the correct amplitudes, and is the correct number of datapoints.

[RavensFan]

This is probably just a weird artifact or bug in the cursor legend.  It so far seems to be just a visual issue and not something that is causing me problems with the data.

But I did notice a pattern as I clicked through the chart one cursor click at a time.  It seems like there is a pattern as to which values show up with parentheses around them.  It is every 9th, 10th, or 19th value.  If there was a way to programmatically grab the actual text that gets displayed in the legend, then I could step through my millions of data points and determine more exactly what the pattern is.

[RavensFan]

After 3 years, I ran into this issue again with a multi-plot cursor.  It seemed familiar, so when I searched for it, I saw it was my post talking about it.

I wonder if anyone from NI can comment on this.  Is this a bug?

[Ben]

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@RavensFan wrote:

After 3 years, I ran into this issue again with a multi-plot cursor.  It seemed familiar, so when I searched for it, I saw it was my post talking about it.

...

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Don't you hate it when that happens?

Spoiler

What is worse is when I call NI and they Google it and send a link to my own thread.

Ben