topic Re: Labview Basic Questions in LabVIEW

Labview Basic Questions

nkritsch — Mon, 08 Sep 2014 12:32:02 GMT

Hello,

i have 2 Questions:

i want plot some plots like this: http://elektroniktutor.de/bauteilkunde/bt_pict/trkennl.gif

now all my plots have the X in the right position. Can i twist it to the left?

If i negate the X Side its looks ok but the X legend is wrong (because its negative).

I haave seen often in NI Programs that they have an run and stop button.

How can i implement this?

the programm runs all time....with start i start the task and with stop i end the task (but the program will still run)

i only yfound the Funcction "Stop" but it terminate the whole session.

Re: Labview Basic Questions

crossrulz — Mon, 08 Sep 2014 12:42:11 GMT

3 Hour Introduction
6 Hour Introduction
LabVEW Basics
Self Paced training for students
Self Paced training beginner to advanced, SSP Required
LabVIEW Wiki on Training

Re: Labview Basic Questions

nkritsch — Mon, 08 Sep 2014 12:49:01 GMT

i have done the 3 and 6 hour introduction....

Re: Labview Basic Questions

crossrulz — Mon, 08 Sep 2014 12:51:00 GMT

@nkritsch wrote:

i have done the 3 and 6 hour introduction....

And they didn't teach you to use a stop button? If you are using the Run Continuous button in the toolbar, stop doing that. Just use the normal run button.

It would help us diagnose your problem if you posted your code.

Re: Labview Basic Questions

nkritsch — Mon, 08 Sep 2014 12:54:33 GMT

i will do it like : http://www.eng.auburn.edu/~niuguof/2210labdev/html/_images/bjt-iv.png

if i press run...the measure start....if i press stop the measure stops.

But the Program runs all the time.

Using the Buttons "run", "run cont." and "stop" i doont wanted to use

Re: Labview Basic Questions

Hooovahh — Mon, 08 Sep 2014 14:13:44 GMT

Hey crossrulz beat me to it.

Back to the posters issues. Yeah don't do what you code is doing. Try what I've attached. It is your program with some improvements. I think the functionality should be the same. Just click Run Once. Then when you want to run click the start button. To stop click the stop button again, or if the condition is met that normally would stop the VI happens, it will stop on its own. Also to stop the application click the close button (the red X) like a normal program. Of course if a test is running the stop will be ignored until the test completes. You can add your own abort test button if you'd like.

Other general comments. Don't use dynamic data types, don't use express VIs and DAQ Assistant. Don't make the block diagram have to scroll in more than one direction. Don't use run continuous. Don't use Abort VI toolbar button or primative.

Re: Labview Basic Questions

Jeff-P — Tue, 09 Sep 2014 17:27:55 GMT

@crossrulz wrote:

3 Hour Introduction
6 Hour Introduction
LabVEW Basics
Self Paced training for students
Self Paced training beginner to advanced, SSP Required
LabVIEW Wiki on Training

Two more useful links that have been recently updated/added

learnni.com (currently just for LabVIEW)

ni.com/gettingstarted (which links to the LabVIEW Basics topic crossrulz suggested)

Jeff Peacock

Product Support Engineer | LabVIEW R&D | National Instruments | Certified LabVIEW Architect

Re: Labview Basic Questions

Hooovahh — Tue, 09 Sep 2014 19:23:40 GMT

@Jeff-P wrote:

Two more useful links that have been recently updated/added

That is fantastic, I'll be adding it to the list of recommended links for new users I post.

Re: Labview Basic Questions

nkritsch — Wed, 10 Sep 2014 08:30:03 GMT

Hello,

thanks to your code

How do you make it that when you "run" the program the front panel appers on a new window?

why its bad to use DAQ Assistant? in the introduction it was told that we should use it.

do you know how i can tell the XY Graph that i dont want get the Axes (of the X or Y) in the one direction, but in an other direction?

Re: Labview Basic Questions

crossrulz — Wed, 10 Sep 2014 11:42:19 GMT

@nkritsch wrote:

How do you make it that when you "run" the program the front panel appers on a new window?

I'm not sure what you are asking here.

nkritsch wrote:

why its bad to use DAQ Assistant? in the introduction it was told that we should use it.

The DAQ Assistant is good for very quick programs where you are just quickly getting some data and showing it on a graph. If you need to do any more than that, go to the actual DAQmx API. The DAQ Assistant has a lot of inefficiencies that doesn't make it good for non-tiny projects. And its output is a Dynamic Data Type, which we HATE. The reason we detest the DDT is because it encapsulates the actual data. You will have no clue what the is just by looking at it. And we've seen some really messed up code because of that.

nkritsch wrote:

do you know how i can tell the XY Graph that i dont want get the Axes (of the X or Y) in the one direction, but in an other direction?

If you weren't use the DDT, I would likely say to use Transpose 2D Array.

Re: Labview Basic Questions

nkritsch — Wed, 10 Sep 2014 12:29:36 GMT

ah ok thanks.

i changed the DAQ inputs to DAQMQ Read.

But now i have 2 different Tasks so my program is slower.

The outputs can stay in DAQ Assistant because thay dont produce dynamic data?

Re: Labview Basic Questions

crossrulz — Wed, 10 Sep 2014 12:41:50 GMT

@nkritsch wrote:

i changed the DAQ inputs to DAQMQ Read.

But now i have 2 different Tasks so my program is slower.

Why? You can have multiple channels in the same task.

I would do the same for the Outputs. Put them all in a single task (this is with the assumption that everything is on just a single DAQ board).

Re: Labview Basic Questions

Hooovahh — Wed, 10 Sep 2014 12:59:40 GMT

Crossrulez has already said much of what I would say. One thing I'd like to add is that you can convert a DAQ Assistant Express VI to a normal VI by right clicking and choosing Open SubVI. This can then show you the code that would normally get ran by the Express VI.

DAQ Assistant, and Express VIs are limited in what they can do. Want to change timing mid test? Well you can't. Want to stop the task and add some more channels? Well you can't. Want to choose what channels to read programatically? Well you can't.

But if the DAQ Assistant meets your needs, and you never need to add requirements to how data is measured, then DAQ Assistant can be used. It was wrong of me to say you shouldn't use it. Just know when it is appropriate to use DAQ Assistant.