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OKors
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Incorrect behavior while using cursors on a zoomed-in signal

I've just recently started using the Cursors function to determine specific values within a recorded signal.

Problem is when I use the Zoom tool (located within the magnifying glass icon under the timescale) to zoom in on a specific peak the cursors malfunction. When you grab a cursor handle and drag it the cursor intersection no longer follows the signal trace in the graph.

 

To recreate:

  • Log a few seconds of data with Signal Express. I always pass the signal through the Amplitudes and Levels step in order to view the signal as a Scope chart.
  • Right click on the graph and select Visible Items> Cursors to add cursors to the graph
  • Use the drag handles to move the cursor's intersect along the signal.
  • Click the magnifying glass under the timescale and select the zoom tool (upper left-hand corner of the box that appears)
  • Click and drag within the graph to zoom in on a signal peak.
  • Now use the cursors grab handle to intersect on the zoomed in peak.
  • The cursors no longer follow the signal trace.

I'm pretty confident this is recreateable since the same behavior exists on both our machines in the lab as well as the 2011 Beta software at my desk.

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise
Member
Roryriffic
Posts: 87
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Re: Incorrect behavior while using cursors on a zoomed-in signal

[ Edited ]

Unfortunately, I was never able to duplicate the behavior you're seeing.  I sampled a sine wave, and no matter how I zoomed or when I displayed the cursors, etc., I was always able to keep the crosshairs following the graphed signal. 

 

Perhaps it's something specific with the signal you're trying to measure. Could you provide a screen shot of it?  Also, at what resolution are you trying to zoom to?  Are you sure the cursors don't follow the graph, or are they simply not able to define the peak you're interested in because of a too-high resolution?

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OKors
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Re: Incorrect behavior while using cursors on a zoomed-in signal

Ive attached some screen shots of the graph and the steps along the way. Also included is the project file.

 

I'm feeding an analog +/-10V signal through the feedthrough panel then scaling it as a load cell.

The signal I'm viewing in the graph is dbl signal from the Amplitudes and Levels step.

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise
Active Participant
OKors
Posts: 225
0 Kudos

Re: Incorrect behavior while using cursors on a zoomed-in signal

[ Edited ]

More attachments

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise
Member
Roryriffic
Posts: 87
0 Kudos

Re: Incorrect behavior while using cursors on a zoomed-in signal

I changed your project files to acquire an analog input for the hardware I have and I still cannot replicate this issue you're seeing.  Can you replicate this problem with other graphs? With other log files? With other SignalExpress projects?  Or is it only with this project and this graph in this particular log file? Which version of SignalExpress are you using? 

 

Also, does this same behavior occur with other zoom methods, or just the one you have outlined (top-left zoom icon)? After zooming in, if you right-click on the graph and disable the crosshairs, then right-click again and re-enable them, do they lock to the graph then?

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OKors
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Re: Incorrect behavior while using cursors on a zoomed-in signal

[ Edited ]

I created a completely new project (still using the same signal as an input). Here's some new results:

If I take the signal straight from the DAQmx Acquire step and add it to the graph I can view the cursors as expected. I can also zoom in using the zoom tool shown earlier and the cursors intersects follow along nicely.

 

If I pass the signal through an Amplitudes and Levels step and drag the DC signal into the graph this is where the problems start. Cursors are normal but once I zoom they no longer follow the signal. This is true regarless of which zoom tool I use.

I should also mention, when zoomed in and dragging the cursors drag handle right and left across the graph I can see the crosshairs following "something". It's not the signal line in its current zoomed scale, it's something else; as if it's following the signal in its original scale, even though the whole graph and signal line are zoomed in and scaled much larger- the cursor's crosshairs are not 'zooming'.

Hope that made sense.

 

When viewing signals I only use scope/strip charts, XY graphs, or the Large Display for a numerical readout. Since I cannot use the native signal from the DAQmx Acquire step to view as a scope chart or XY graph I pass it through the A&L step. As such, I will likely never use just the raw signal from the DAQmx Acquire step. It will always be turned into something I can view as scope/strip or XY graph; hence the need for the A&L Step and where the issue seems to generate.

 

The crosshairs do not lock onto the graph if I disable/re-enable them.

Check my signature for current hardware/software versions. Also attached is a screenshot of the MAX's device drivers list.

 

 

 

 Thanks for your help too btw.

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise
Member
Roryriffic
Posts: 87
0 Kudos

Re: Incorrect behavior while using cursors on a zoomed-in signal

OKors, I still cannot duplicate this issue you're seeing.  I've tried all of the things you've listed in your posts, but still no luck.  Could you list out the exact step it takes to cause the problem you're observing?  If this is a bug you've found, it could be very specific to what you're doing.  In addition, you may try repairing SignalExpress 2010, as part of its installation could have been corrupted in some way.  You can run a repair by going to the Control Panel » Programs and Features » National Instruments Software » Uninstall/Change » NI LabVIEW SignalExpress 2010.

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OKors
Posts: 225
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Re: Incorrect behavior while using cursors on a zoomed-in signal

Okay, I've discovered a few step details that may determine why you have not been able to replicate the issue on your end.

The main step which seems to make or break the cursor issue is whether or not you view the graph as a strip chart or scope chart. Changing the Update Mode to Scope Chart is where the issue seems start.

 

This time I simply created a 0.5hz Sine wave (Create Analog Signal step) and passed it through the Amplitudes and Levels step. Here are the detailed steps following the creation of the sine wave:

 

  • Drag and drop the Sine Wave DC signal from the Amplitudes and Levels step into a graph
  • Change the Update Mode to Scope Chart
  • Run a few seconds of data
  • Select Visible Items... Cursors to enable cursor view
  • Drag the cursor around; the cursors crosshairs should follow the signal
  • Use the lasso zoom tool (upper left icon in the zoom tools box) and zoom in on a few valleys generated by the sinewave
  • At this point the cursors should fail to lock onto the signal. 

If what I've outlined above does not cause the issue try this:

  • When zoomed in use the "pan tool" (hand icon below the time history) to drag the signal around. Drag it from the peak of the sine to the valley, or just 'shake' the graph side to side a little.
  • Now see if the cursors loose the signal.
  • If not...
  • Change the History Length to 5000
  • change the x and y scales back to autoscale and re-acquire a few seconds of new data with the above History Length changes in affect.
  • Repeat the process starting from bullet point 4

With the actions detailed from above I am able to recreate the issue on both our lab PC's running identical hardware and software, as well as the cDAQ at my desk running Signal Express 2011 Beta.

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise
Member
Roryriffic
Posts: 87
0 Kudos

Re: Incorrect behavior while using cursors on a zoomed-in signal

Thanks for providing those steps! It is greatly appreciated and very beneficial.  While I wasn't able to duplicate this issue exactly as you have described, I did get to a point where I noticed strange behavior with the cursors.  Depending on where and how I zoomed into the graph, I could get the cursors to "think" they were following a signal, when in fact this was the incorrect signal.  What it actually was was the larger zoomed out version of the signal that the cursors were trying to follow.  So, bottom line as you described it, when you zoom in to a particular level, the cursors don't follow the zoomed in signal.

 

Also as you mentioned, this behavior is only viewable with a scope or sweep chart, as I could not duplicate it with a strip chart.  This is most certainly a bug and I've filed it so to R&D.  Unfortunately, there's no workaround at this time, except to use a strip chart.  I'm sorry if this causes any inconvenience, but hopefully R&D will be able to resolve the issue quickly. I will try to post with any updates I have.

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OKors
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Re: Incorrect behavior while using cursors on a zoomed-in signal

Rory,

Thanks a lot for your patience while trying to isolate this issue. I'm glad you were able so see some sort of stange behavior.

 

You describe exactly what I'm seeing on my end. If you zoom in far enough the cursors "think" it's following the signal when in fact its a ghosted signal left over from a previously zoomed resolution.

 

The workaround is to change the graph to strip chart momentarily while I use the cursors, then back again to view the live data.

 

This is not much of an inconvenience but I'm glad we can document it as a bug.

 

Thanks!

SCXI- 1000 Chassis w/ 1346 adapter
PCI 6281 DAQ card
SCXI- 1520 Bridge Board w/ 1314 Terminal Block (x2)
SCXI- 1180 Feedthrough Panel w/ 1302 Block
Signal Express 2012.
Win7 Enterprise