Different results from MAX and Labview

[jyuan]

Hi all,

We did an impact testing a couple of days ago, and I got very big acceleration (the peak is about 300g, which is much larger than the estimated value).

And then I tried a small imact test in the lab using a steel plate which is less than 1 lb to impact a steel ruler, I still got big peak number (more than 200g, which is impossible). And then I tried the small impact test again by using MAX, the peak number is about 12g, and the curve seems like pretty reasonable. I was wondering why I got different results by using MAX and Labview?

Also, sometimes when I connect the SCXI-1001 to the computer, it says the USB is malfuntion and cannot be recgonized by the computer, and turns out the driver file does not exists. But most of the time, it works very well and the driver file does exists. Why this happened?

Thanks.

Yuan

[crossrulz]

This sounds like there is a scaling issue here.  Can you show your code and screen shots of your MAX setup.

[jyuan]

Hello,

The attached files are the code and screen shot of MAX setup

[Hooovahh]

So much DDT and such a large BD.  Do objects need to be spaced out so much?

Back to the original question, is there a reason why you aren't creating these virtual channels or tasks in MAX, and then just using them in the application?  I mean is there a reason you don't just use the exact task that MAX uses instead of making new ones?

EDIT:  are you also aware of the print screen button in Windows?  This saves the screen as an image and puts it in your clipboard.  It makes for smaller pictures too since that one was 4MB.

[crossrulz]

Hooovahh has a good point.  Just use the task that you created in MAX.  That would save a lot of your coding and make it a lot easier to read.

[jyuan]

Hooovahh,

Thanks for the advice. Well, when I first learned how to use NI to obtain data several months ago, my groupmates all used Labview programming to record data. And I simply used MAX to check if my sensors are working. At the same time, I don't know if I understand it correctly, MAX can only group one type of sensor together, but I want to clike one "run button" and get data from strain gage, LVDT, accelerometer at the same time and our tesing duration is just about a few seconds. And also I didn't find a place where I can record the data in MAX

Thanks,

Yuan. 

[crossrulz]

---

jyuan wrote:  but I want to clike one "run button" and get data from strain gage, LVDT, accelerometer at the same time and our tesing duration is just about a few seconds. And also I didn't find a place where I can record the data in MAX

---

You can do that.  A task can only have the same types of inputs, meaning Analog Input, Analog Output, Digital Input, Digital Output, etc.  Different sensors are just read with Analog Inputs.  So they all can be in the same task.  In MAX, just set up a task a configure each channel as it should be.  Then use that single task in your LabVIEW code.

[jyuan]

Ok, so after I create a task in MAX, I run it in MAX? But how to record data, I can see how the data appears in the graph but how to record all the data. And I am a little confused here, you said I can create a task in MAX and then use it in the Labview code? How to combine them together?

Thanks.

[crossrulz]

In LabVIEW, there is a DAQmx Task constant/control you can use.  It looks a lot like an enum or ring.  It will have a drop down in order to select which task you want to use that has already been configured in MAX.

[jyuan]

Thanks.