actual time recording (computer performance problem?)

[jayy]

I'm a beginner.
I'm recording the output file in every second, but the time of output file is different from the actual time.
I'm wondering if this is due to the computer performance (450MHz, 128MB) or if vi program can be implemented. I attached the file I use. The problem comes up when I use a vi with 50 channel outputs, but doesn't come up if I reduce the channels to around 20.
Thank you.

[JaredA]

It sounds like you are certainly running into timing issues. I see that in your VI, you use AI Sample Channel to acquire data from a single channel everytime the loop iterates. This is not the best means to go about doing such. The reason being that each time the VI is called, it has to setup the operation, then perform the read, and then clear the operation. What you should be doing is setting up the operationg outside the loop, perform only reads in the while loop, and then clear the task after you are complete. LabVIEW gets shipped with several examples that behave just this way, you should look in the example finder for these.

Additionallly, if you read the help on AI Sample Channel.vi, it states it does a single, untimed measurement of a channel. Since
you posted with the title "actual time recording", I feel that timing might be of importance to you.

You never did mention what version of LabVIEW you have, or the hardware and drivers you are using, so I am leaving this post rather general. If you have some more questions after reading through this post and looking through some of the examples, post back to this discussion with more information, and I will try and help you out further.

Sincerely,

Jared A.

[jayy]

Thanks for the help.
I looked up the example in Labview, I found AI Config., AI Read, and AI Clear in some example. Are these the things you mentioned? However, I couldn't find those in Functions Palette. I'm using LabVIEW v.5.1.1. and SCXI-1001.
Another question is,
If I upgrade my computer, the problem will be solved?
Thank you.

Regards,
jay

[JaredA]

If by "upgrade my computer" you mean that you have the option to upgrade LabVIEW and your OS, by all means do! I do not have LabVIEW 5.1.1, nor a version of DAQ that supports it, so I will try and help you find those VIs, but it could be different.

There should be a sub-palette on your functions palette (note you must be on the block diagram to view the functions palette), where all of the data acquisition VIs are placed. Browse through that (it might be called NI Measurements, NI-DAQ, or something similar). If you are still unable to locate those VIs, but you were able to locate them on an example program, then you could just copy them from the example program and paste them into the VI that you want them to be in.

Let me know if this helps.