Negative time value in daq ai data

[rogerspass]

Hi. We have a PCI-6024E DAQ card. I tried to collect pressure signal data by daq assistant and save to LVM measurement file.

While I look into the data, how comes sometime the time value is negative?

It's in continous sampling mode, and the sampling rate was set to range from 1K to 6K. All appear the same symptom. 

It's randomly happen in a "number of sampling" period. For example, if I set number of sample to 100 (the default value in daq assistant)

then I will sometimes have 100 of negative time value in the saved lvm file.

I have tried to do a clean install of xp systems to eleminate the system instability. But it still happen.

I have read this post: http://forums.ni.com/ni/board/message?board.id=250&message.id=29140&query.id=99714#M29140 

Do anyone ever know this before? Where should I check further?

Will it because of the computer motherboard or the DAQ itself (it passed selftest in MAX though)? 

I attached the vi and the lvm (in txt) file for reference.

Thanks.

[rogerspass]

To quickly point out the negative period in the file, please look into 1st column, while time is beween 9.599~9.700, or 13.299~13.400 or 16.999~17.100 etc. Thanks.

[Hueter]

Roger

Does it happen the same way every time, differently everytime or is the problem happen infrequently?

I ran your VI on my system and was unable to produce the error. Does it behave the same if you change the sampling rate, or samples to read. It seems the number or negative time values = the number of samples to read. Also the negative values are happening at regular intervals so at least there is a pattern.

Also you could try this with a Express Simulate Signal VI so you can see if the problem is in your write to measurement file or in the DAQ Assistant.

What version of LV?

What version of DAQmx?

[rogerspass]

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Huter wrote:

Roger

Does it happen the same way every time, differently everytime or is the problem happen infrequently?

I ran your VI on my system and was unable to produce the error. Does it behave the same if you change the sampling rate, or samples to read. It seems the number or negative time values = the number of samples to read. Also the negative values are happening at regular intervals so at least there is a pattern.

Also you could try this with a Express Simulate Signal VI so you can see if the problem is in your write to measurement file or in the DAQ Assistant.

What version of LV?

What version of DAQmx?

---

Hi. This problem seems only happen on my specific computer with windows xp (with sp3) only. It runs ok on another computer with same mainboard and vista os.

You are right, as I posted the number of negative is equal to number of sample that been set. Do you think will this be a buffer problem?

My daq card is pci-6024E (Dev1) and I create a simulated pci-6024E (Dev2) for testing my program first. 

I noted that my simulated daq card in MAX cannot run! How comes? It pass self test though. The systems will hang after I create max task and run it...

I looks like these two symptoms are correlated.

I will try to rebuilt my system with vista to see if this happen or even try xp with sp2 only.

Following is my spec:

Mainboard: Asus M2A-VM

RAM: OCZ 1GB x2

OS: XP with built in sp3 (not from upgraded)

Labview 8.5.1 academic

DAQmx 8.7.1f2

Thanks for your reply. I will keep you post after my test. This problem is just so weird!

Rogers

[rogerspass]

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Huter wrote:

Roger

Does it happen the same way every time, differently everytime or is the problem happen infrequently?

It happen infrequently.  Well, I would say it will not happen all the time, but if it occurs then it will reproduce continuously.

I ran your VI on my system and was unable to produce the error. Does it behave the same if you change the sampling rate, or samples to read. It seems the number or negative time values = the number of samples to read. Also the negative values are happening at regular intervals so at least there is a pattern.

They behave the same if I change sampling rate and # of sample.  

Also you could try this with a Express Simulate Signal VI so you can see if the problem is in your write to measurement file or in the DAQ Assistant.

What version of LV?

What version of DAQmx?

---

[Hueter]

Roger

I have been unable to reproduce this error on my system, so I am having trouble troubleshooting this.

The next thing I would try is use a Simulate Signal Express VI instead of your DAQ Assistant, and see if you can reproduce the error. This way we can see if the problem is coming from the DAQ Assistant or the Write to Measurement File.

Also does the error persist if you recreate this VI, It could be a corruption problem.

Let me know how these come out

Hunter