waveform chart clears randomly

[e-Cash-Money]

Thanks for posting the proper version Randy.

I just finished converting the example to 6.1 without realizing that Randy had already done it so I will post it anyway. I rebuilt the VI in 6.1 so it shouldn't give you any errors related to version conversion.

Hope this helps,
E.Lee
Applications Engineer
National Instruments

[cviuser167]

Thanks. I had just finished copying the diagram from Randy's just moments ago and was running it . I'm in the process of updating my original app now and will post an update in a bit.

[cviuser167]

I finally got around to making the mods to my app to use the calculated time offset. The chart no longer randomly resets itself!

However, I have this loop running in parallel with an analog input loop that is sampling data from a PCI-6036E card and after some time of running, the two charts are getting noticeably off in their time stamps. I'm thinking my serial device isn't really running at 75 Hz but only close to 75 Hz.

Oh well, I'll have to see what the end user wants before I push on.

Thanks for all the help!

-dennis.

[e-Cash-Money]

Hello Dennis,

I'm glad to hear the chart does not reset anymore 🙂

In regards to the drifting timestamps... One thing you could do is occasionally update the timestamp for the serial data. If the serial data is lagging behind the data acquisition, just grab another timestamp using the Get Date\Time in Seconds VI. If the serial data is ahead of the data acquisition, then it is a little trickier. We would have to decide what the final timestamp on the data should be, how many samples of data we want to place back on the chart, and then calculate what t0 is based on the previous information (we would also have to save the chart history in the while loop. However, if you are also artificially creating the timestamps for the data acquisition, we can just update the data acquisition timestamp if the serial data is outpacing the data acquisition. But like you said, it is ultimately up to the end user.

I hope everything turns out well!

E.Lee
Applications Engineer
National Instruments

[Rut]

Eric,

Thanks. Your modified example helped me. I had a similar problem that the strip chart kept clearing itself and started over again. Now it's gone after consulting your solution.

Rut