Hello!
I am quite new to labview and was asked to
write a program which uses the realtime tools. The program itself is
simple, it is just about giving a specific voltage out and read the
incoming voltage "response" (the interface is a PCI6035E card), but the
whole thing should go as stable and especially as FAST as possible.
Unfortunately
no one in my working group has ever worked with realtime in labview, so
even though maybe the bugs have nothing to do with the realtime issue,
I am getting no satisfying answers around here. Please excuse the
"german/english" mix in the naming of the variables etc.
Now
to my problem: To make sure the program runs as stable as needed in the
specified time, I inserted all of the "finished late?" buttons of the
subVI, to immediately be informed about if there is anything late. If I
start the program, for the first characteristic (it's about a plasma
characteristic, measured by a langmuir probe) it all works (excpect for
one or two little mistakes, which I wasn't able to locate, or rather
wasn't able to find out WHY the timed loop is late), but if it comes to
further characteristics(=Kennlinie, the value is set in the front panel
by "Kennlinienanzahl"), at about the middle of the measurement suddenly
the whole subVI seems to randomly get late, then it continues with
being in time, up until the middle of the next characteristic.
I
know the "finished late" is linked to the setting of the deadline, so I
tried to solve the problem with enlarging the deadline, but the problem
remains, even though it gets a little better. But since I am trying to
make the whole program as fast as possible, the enlarging of the
deadlines (and in respect the encreasing of "start"-time for the next
frame) seems to be counterproductive.
My next suggestion
was that probably the data are passed on way too slow, or that there
was something interfering, but I couldn't locate this mistake either. I
read a lot about local/global variables, queues, and other
possibilities of storing the data and also passing it on in the VIs,
but I wasn't able to find out which solution is the best for my
program.
I have attached screenshots of the
program (characteristics_1 is the main VI, characteristics_2 the
subVI), if that will not be enough to solve my problem, I could also
attach the whole VIs.
Since I am new to LV, I
hope I will get some constructive ideas how to improve the program and
I apologize for the common mistakes I probably made.
Many thanks in advance,
Hanna
