DAQ Assistant issue

[RavensFan]

I still don't know what you mean by "resets".  What values are you seeing "reset"?

[mkatsiou]

You can see it in the excel sheet from my original post, the values will start at 0 and slowly build up to the actual value, stay there for a while, then reset back to zero and build up again. This happens for both the recorded load cell values and the recorded string potentiometer values. ex) 0,10,20,30,40,50,60,70,80,90,100,100,100,100,100,0,10,20,30,40,50,60,70,80,90,100,100.... 

[RavensFan]

Okay.  Now I see.  You are logging from within the DAQ Assistant.  I was looking for a section of code where you do loggin and didn't see any.

In your Excel file, I don't see anyting going from 0 to 10, but from 0 to about 2.45 +++++   in your first column.

Logging from within the DAQ Assistant is a relatively new feature.  I'd recommend that you don't do it there but drop a separate Write to TDMS File vi in your diagram and use that to do the logging.  While Express VI's are great for getting some code up and running quickly with some basic configuraiton, they are also somewhat limited in what they can do.  And the "reset" maybe one of those, or it may be a bug within the Express VI.

[mkatsiou]

The "0 to 10" was an example, in retrospect I shouldve used the same values as the excel document I shared...

I'm very new to LabVIEW, other than the "intro to programming" I took in school, which gave me MAYBE 5 hours of LabVIEW experience, this is my only work with it, so I don't really know how else to log data... I'm sure there's tutorials, I just didnt realize there was an alternative way to log...

[WestOfEden]

Just to clarify, is the output of your device supposed to be constant? I don't know offhand why the readings would be ramping up and then going back to 0 and repeating. Do you have something else like a DMM you could use to verify the output of your instruments?

[mkatsiou]

Yes, the output was supossed to be constant at about 2.6.

After more investigating, I'm starting to think the issue may be with my wiring/sensors rather than the NI unit or program.

[mkatsiou]

So, I was using this program with a load cell and string potentiometer, and was getting this issue where it seems to reset. Then I tried hooking this up to a waveform generator and this issue wasnt present, causing me to think that the issue was then my hardware, not software.

However, this "reset" occurs whenever I reach the "samples to read" quantity specified in the DAQ Assistant, so if I change that quantity to 20, then I see the "reset" every 20 samples, if I change it to 100, then I see the reset every 100 samples.

I have an external excitement for my sensors, so it's not like the NI unit is resetting a signal to them, it just seems to reset its scanning for data?

Could the DAQ Assistant and while loop combination be causing this?

[WestOfEden]

I'm not sure offhand why you would be seeing the values dip every time the DAQ Assistant starts reading the next set of samples. I'll see if I'm able to find anything out about that.