Data acquisition trigger

[Setu]

Hi all,

I am new to labview and have (again!) encountered an obstacle where I need some advise.

I am designing VI for dynamic data acquisition with a sampling rate of 200-400 samples per second. I will be reading accelerometers on all 12-16 channels. I will need to trigger the acquisition when one (or more if possible) accelerometers reach a certain value and then record data for say 30/60 seconds. In that 30/60 seconds I want to see the data that is being recorded, in a graphical display, fair to say in real time. How can I do this?

Do I need to use hardware analog triggering? or can I achive this programatically without any loss in data since I am sampling at such a high rate? I used AI Read.vi with conditional retrieval quite su
ccessfully to obtain 30 seconds worth of data at 200samples/s, but I could not see the data as it was read. I only saw it after 30seconds, thus defeating my purpose.

I think my card (PCI 6023E) is not capable of analog triggering. If this is true I'd appreciate if you could recommend a card(s) that is. I will be willing to buy a new card and additional any hardware/software cost permitting.

Here is the hardware I have:
- PCI-6023E
- SCXI 1000, 1100, 1300
- Labview 6i.

Thanks to any and all who are willing to help.

Regards,
Setu.

[Sastry V.]

1. You need to do Analog Trigger, the triggering signal will be the signal available at the accelerometer.

2. You need to use a card that supports Analog Triggering or you can use conditional retrieval too.

3. If you want to acquire 30 sec worth of data, at 200 samples/s, then set the total number of scans to acquire to 6000 and the scan rate to 200.

4. Please take a look at the examples on Data Acquiistion Analog Input at National Instruments website. The link is given below:

Data Acquisition

[Setu]

Thanks for the reply guys.
See, I also want to view the data while it is being acquired. Currently using conditional retrieval the AI Read.vi locks out labview until 6000 scans are complete. I want to see every point as it is being acquired. Is this possible?

[test1]

Setu;

Use the Labview shipping example named Acquire N scans Analog Hardware Trig.vi, so you can make sure the Software part works. There are a couple of gotchas though. First, the triggering channel must be the first channel in the scan list and must also physically be the first channel in the SCXI module. Second, when the trigger channel control is left empty in LV, it works perfectly.
Hope this helps.
Filipe