Why are traces drawn incorrectly when zoomed out on HyperTrend graph?

[Chris_K.]

Frequently when viewing historical data from a citadel database using the HyperTrend graph I observe false features on the traces. These features will disappear when zooming in on the graph. The attached document has screen captures. Could this be a video card/driver issue? I have observed the problem on several computers, each having different hardware.

[Remzi]

Hi Chris,
It seems that there is no actual data point at 1:55 PM and You can check the historical data in Excel to determine if is there any data at 1:55PM. Here's the link to the on-line document that explains this process.

http://zone.ni.com/devzone/conceptd.nsf/webmain/59A3A3A9FC54591F8625680800731979?opendocument

Or send the database to (ftp://ftp.ni.com/incoming/) then I can look into this. Which version of LabVIEW DSC are you using? do you see the same behavior in MAX when you create a Historical Data Viewer?

Regards,
Remzi A.
Applications Engineering
National Instruments

[Chris_K.]

Remzi,
I'm using LabVIEW DSC 7.0. I'll be able to look into this later this week and will try exporting the data to Excel to see what the raw data looks like. I'll let you know what I find out. Thanks

[cs42]

I can't give you an explanation, but I have this problem too (LV DSC 7.0). The plotting in MAX is not always reliable esp. if you use XY or YX steps. It happens sometimes that features are shifted in time. If you change the zoom these shifting may disappear or not. With line style "Solid" there seem to be less problems but if you have very infrequent point (some minutes) this may lead to a false (human) interpretation of the data.

So long,
Carsten

[Chris_K.]

Remzi,
I tried to use the Excel import method, but received errors. (I think because the trace name is too long.) Instead, I used the "Read Trace.vi" to get the raw data and plot it on a LabVIEW XY graph. The LV graph does not show the problem observed on the HyperTrend. After running this VI, I made current values default so you can view the data on the graph without running the VI.

I have also archived the trace in question to its own small database. The database, the VI, and some HyperTrend screen captures are including in the attached zip file. Thanks.