Fix waveform chart blinking to zero bug

[patrickpollock]

Waveform charts are really useful but have an annoying bug. Every now and then (maybe once every 10 seconds depending on the update rate), the digital displays blink to zero even though a zero value was never written to the chart. I use these charts frequently in HMI type displays and explaining this behavior is always part of the training for new operators ("Don't worry if this critical sensor goes to zero for a second unless the line on the chart also goes to zero, then you should freak out and hit E-stop"). This has been brought a couple times over the last 8 years (http://forums.ni.com/t5/LabVIEW/Waveform-chart-digital-display-blinks-zero/td-p/554868) but has never gained enough attention to be fixed. I know this functionality could be duplicated with additional numeric indicators or even an xcontrol but I would prefer to just have waveform charts function correctly. I attached a VI that shows this behavior. All three of the digital displays randomly blink to zero.

[altenbach]

Seems like a bug report, not an idea for a new feature.

[X.]

Good luck with getting any traction on the Graph objects...

[patrickpollock]

altenbach, I agree that this should be a bug report. From the post that I linked to (take out the last parantheses to get the link to work), a bug report was filled out in 2007 but it was never fixed. I was hoping that if enough people support this idea on the idea exchange, it may become a priority. 

[ToeCutter]

K+

[JimChretz]

I slightly modified your VI to read that digital display value from property node and noticed the property node returns an error at the same time that one or more plot shows 0.

[JimChretz]

If you wire this way, the bug won't happen.

[patrickpollock]

Jimmy, thanks for posting those VIs. That property node behavior is really strange though it's nice to have a way of testing for this behavior. From you second VI, it looks like this bug is limited to charts with a "waveform" type. I suppose I'll convert my charts to this "cluster of doubles" type to get around the bug. Some of the charts on my UI only get async data (dt isn't constant) so the waveform type is really nice because the data spacing on the x-axis is handled automatically. I'll probably just set the chart update rate to something constant but faster than my fastest async rate and just push data to the charts that is sometimes duplicated.