Write LabVIEW Measurement File. Problems with the x-column timestamp

[rberger]

Hi All:

This is my first crack at the LabVIEW Measurement File Express VI. I can configure, convert the express VI and then place it in a DAQ loop to store results. Things work great. But what if I want the timestamp to reset to zero after calling the DAQ loop everytime? At the moment, the timestamp keeps appending time relative to the first call of the Measurement Express VI. This means I have to exit my application to reset the timestamp to zero. In my app, the user will perform several starts and stops of the DAQ loop. I would like the timestamp to reset to zero on the first measurement everytime I call the DAQ loop without quitting my application. I've been messing around with several of
the converted Express Measurement VI flags without any results. Has anybody had any sucess?

Robert

[Jeremy Braden]

Can you post simple code that shows the problem and your version of LV?

I figure the behavior your are seeing can be caused by two things: the timestamp of your acquision, or Write LabVIEW Measurement File itself.

Are you starting and stopping your acquistion with every write? You may be passing a relative timestamp to the function.

Write LabVIEW Measurement File is really easy to use because it does not give the programmer many options. The behavior your are seeing may be just how the function was written. You may need to do parse the data and write it to file yourself. This way you can get any behavior you want. Although this is fairly straight forward, this method will a few hours to implement if you have never done it before.

[rberger]

Attached is a jpeg image of the data acquisition portion of the program I am running.

The DAQ loop is the right side while loop within the case structure. Notice I do call DAQmx Clear Task after exiting the DAQ loop.

I believe the Measurement Express VI is the culprit. I am still looking into it.

Robert

[rberger]

OK. I figured it out.

In the Measurement Express VI, one has to be able to get to the Reset Boolean flag within the ex_subFileWrite.vi.

That is the easy part.

The non-trivial modification is after going several subVIs deep, one has to set the ex_SetExpAttribsAndT0.vi to NON-REENTRANT.

After doing this, everything works.

If there is a better way, I would like to know!

Robert