ulx sampling

[MKNU]

Hi,

I am completely new to Labview itself and have to use it with an Omega daq. I tried doing a simple program to collect the temperature data. I am getting inaccurate time readings. Can someone please explain? I am trying to get the samples at an interval of 6 seconds for 2 mins to just test the program.

Both the measurement file and labview files are attached to this for reference. Really appreciate it.

Thanks,

MK.

[MKNU]

Hi! I also wanted to add some extra information.

I am trying to calibrate thermocouples and the daq assistant is reading temperature from the RTD which I am using as a secondary reference.

[Taki1999]

I don't have any ULx devices so I can only be of limited help.

I would suggest configuring your task outside of the loop and clearing your task outside of the loop.

Reconfiguring and clearing your task each time through the loop probably throws your timing off and isn't necessary.

[MKNU]

would configuring task include taking the sample clock out of the loop?

[Taki1999]

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@MKNU wrote:

would configuring task include taking the sample clock out of the loop?

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Correct. The only part inside the loop should be the Read.

[MKNU]

That has changed the x values from that of seconds to a the sample number. I need x values to be time. In the actual experiment I need them to be time stamps.

[MKNU]

Hi

I just wanted to let you know what I figured out. I put the configuration of task and clearing out of the loop. This meant that the sampling clock was also out of the loop. But the delay vi was still inside the loop. This made the samples late by specified time. But the sample clock did not realise that it was being triggered after a time delay and counted time at the rate specified instead of the real time when it was triggered. I therefore, made a single input to sync the sampling rate with the delay.

I think this has worked very well. I am getting expected results with the time in seconds as well as with time stamps.

I still got a problem though. When I try to reduce my sampling rate to less than 1 sample per 8 seconds, it tell me that I cant do it because my device has a lower limit set to 0.124Hz. Is there a way around this?

Thanks for your help.

I really appreciate it.

MK. 

[Taki1999]

For that slow a rate, you may not be able to use HW timing.

You might try taking a single SW timed sample at specified intervals. You'll end up stuck with the standard limitations of SW timing so you may not get the precision you want.

Another option would be to HW sample at 0.125 Hz and throw away the data you don't want.