Data points disappearing on graph windows...

[orientite]

Hi
During the acquisition of a large amount of data from a DAQ-board (PXI-6229), I visualize these points on a graph.
Sometimes, the whole graph window is cleaned then data begin again to be displayed.
Why ? Is it due to a problem with a window buffer  (I use a history graph with a big history buffer) ?
Thanks

[chrisger]

hi there

are you sure you use a GRAPH? you said "I use a history graph with a big history buffer", so i think it's rather a CHART.  if this is the case play around with the Update mode (right click the control on the frontpanel->Advanced->Update Mode)

try to use the "Strip Chart" Mode.

[orientite]

Hi
I actually use the "strip chart".
In fact, there is no trouble when I run the vi for the first time.
The problems seem to occur as soon as I begin to manipulate the windows (displaying the diagram, or displaying another application while the LabView vi is running...).
So I suspect some kind of screen buffer to be involved... Any idea ?
Denys

[chrisger]

hi there

hm, well...

we need some more information:

- how many graphs do you display?
- what's the datatype?
- how deep is the history?
- how many RAM do your computer have?

as far as i remember the chart control allocates twice the history - memory as a continuos area of the RAM. so:

- how many RAM is still free when running your Apps?

please post some code if possible.

[orientite]

Hi Chris
Thanks for your attention.
Currently I use 3 different graphs (strip charts). On each I plot several channels (between 1 and 16) (datatype is DBL arrays). I acquire 1000 numbers per second per channel. The history is 40000.
When I run the vi , the windows can display as much as 1 mn of data, so 60 x 1000 x 16 points at most (I put the x-range to 1 mn). Then the data begin to enter into the history. When the trouble come, the display cannot keep more than 5 or 10 seconds before cleaning...
The computer has 2 Go RAM.
So ???
Best regards
Denys

[chrisger]

hi there

i once build an app with 16 x 16 charts, history depth 36.000 (P4 1.7 GHZ, 1 GB RAM), datatype SGL. so i think it's not an memory issue (as long as your machine has enough memory free!), but: try to switch to datatype SGL anyway (memory usage is cut to 50%!!)

please post us some code or screenshots (i'm off the screen for next 16 hrs)

[orientite]

Hi
Thanks for your suggestions.
I tried using SGL instead of DBL numbers, but the same troubles occur.
I tried too using the express vi "sample compression" to reduce the number of points by a factor 10... but I get the same troubles.
Here attached is a copy of the screen. There is about 6 s of measurement displayed (the history buffers are still empty), and the 3 chart screens cleaned some seconds later.
Sometimes more than one minute is displayed, so that the history buffer begins to be filled. So the troubles do not depend on the history buffers since they are empty when the trouble occurs.
It is difficult to post the code since it is a big diagram with a lot of functions and connections.
What I'm doing :
I acquire about  30 channels from 3 DAQ boards, in binary mode (I16). I always plot these data on 3 distinct chart screens (see attached file) after a renormalization to obtain floating numbers in volt from 2 bytes numbers.
Is there some buffers involved in this renormalization and display ? How to control these buffers ?
Regards
Denys

[chrisger]

hi there,

sorry, i don't get this. we need some code, otherwise we can't help you.

[orientite]

Hi
Attached is the code.
Regards
Denys