Turn off XY plot display

[g4danny]

Hi,

I am collecting data from two voltmeters, a temperature controller and a digital lock-in amplifier (sometimes also a magnetic field controller) via GPIB using LabVIEW 6i on Mac OS 9. I am using three XY plots to display the data during acquisition: two plots of the voltmeter data streams (V1 vs V2 in two different scale setings) and Lock-in vs. V2 plot. I am using buffers that hold all data (increasing length), since upon every new point all the plots are redrawn. This consumes a lot of time, but my main concern is that with growing amount of data stored and displayed the time taken to handle the buffers and update the plots is increasing, hence lowering the "sampling rate". The density of data points may drop to 50% of the starting one, when ~5000 points are handled.

It may be an elementary thing, but I haven't succeeded in making the VI so that I could turn on/off the updates or the display of the plots. What I tried was to create a control out of a plot's Property Node attribute (like "Visible"), but the control didn't have any effect.

I don't think there is any way of plotting the XY data without the need to carry increasingly large buffers. Is there any way to turn off the updates and only update the plots (one-shot) upon a push of a button? The data acquisition drop-out due to such "flush" is not a problem for me.

Thanks in advance!
Daniel

[altenbach]

First of all, you should not grow buffers without bounds. Initialize a fixed size array (e.g. initialized with all NaN) and feed in your new data at the correct indices using "replace array subset". Design it as a FIFO with fixed size.

To limit the updates of the graphs, place them in a case structure that only turns true a slower intervals or on demand.

[g4danny]

Thanks you, I am working on all the suggestions. I am making the "NaN" initialization through a ratio 0/0, as I have not found a "NaN" constant. I think I know how to do all the rest, so thanks a lot for the advice!
Daniel

[altenbach]

Just create a numeric diagram constant and type nan in it. Voila! 😉

[g4danny]

Excellent, thank you!
D.