pci 6229

[Deznium]

I have a PCI-6229 card (for data acquisition) setup and configured on my PC and it passes all the tests and seems to run fine. So, what I wanna do is to input 4 analog signals to the analog inputs of the card and acquire data (simple as that). But I only want to start acquiring data at a particular instant. This is what I want to do: I want another computer/device connected to the PCI-6229's I/O pins sending signals to the card telling it when to start and stop acquiring data. So, for eg. the computer/device sends a TTL pulse to the I/O of the card to start acquisition. I want the card then to continuosly acquire data untill another TTL pulse is sent to stop the acquisition. I was wondering if this can be done in LabView? and if yes, are there any similar examples I could look at somewhere? any hints on what I need to do etc.?
I have LabView 7.1 with DAQmx driver and DAQ Assistant.

Any help would be greatly appreciated..

Thanks!

[reddog]

I believe this similar post addresses your question. I've also attached the VI here that is similar to the one shown in the linked post.

[Deznium]

I'm just trying to read and sample an analog signal at the moment without the start/stop trigger. So, I have a signal going into my PCI-6229 and I get nothing when I run the file. I tried almost everything I could and I think the file is perfect as well. Anyways, I've attached the file with this message and if you find anything wrong or I need to change anything, please let me know.

[reddog]

Without the triggers, your modified VI will only acquire 4 samples and stop. If you want to continuously acquire signals without the triggers, I recommend using one of the shipping examples. You can find the shipping examples by selecting Find Examples from the Help menu in LabVIEW. From there, navigate through the following directories: Hardware Input and Output->DAQmx->Analog Measurements->Voltage. The Cont Acq&Graph Voltage-Int Clk.vi example should work for you.

[Dr._Imad]

your vi is set to read 4 scans at a rate of 10 000 Hz and stop. you are probably reading something. Increase the number of scans to read and you will see the readouts

what kind of input are you measuring, DC ?

[Deznium]

thanks for your help.
I'm reading an analog signal with a frequency of 5 Hz. I've actually got it to work partially, I had to change the sample clock type to "continuos" from "finite". I'm reading some random signal at the moment, I think the number or samples to be read and the sample rate is not set right. Also, what if I want to acquire 5 signals continously and simultaneously, what do I need to add in my labview module? I know that labview scans through the analog channels at a specified rate to acquire the signal. So, in such a case, are my acquired signal being captured simultaneously?
Thanks again

[Dr._Imad]

as Reddog said, follow one of the sipping examples

the sampling frequency should be set at least 10 times the maximum frequency content iof the sampled signal (twice using Nyquist criterion)

so, you may set the sampming rate at 1000 Hz (should more than satisfy the 5Hz signal)
If you then put the number of samples to read at
200, you will get 5 updates per second
500, you will get 2 updates per second
1000, you will get 1 updates per second

etc

[Deznium]

Hi and thanks for all your help guys. I'm still unable to figure out what's wrong here, I've attached the .vi file, if you happen to have some spare time, please try to go over it (if possible).
So, I'm trying to measure a 5 Hz signal (same as before).
The frequency in the front panel is set to: 1000 Hz
The samples per channel: 200
The samples per read: 200 ----- Not sure what this exactly means
When I run the test panels, I get a very good signal.
It's either the way I'm sampling the signal or there's some minor problem in my labview schematic.

Thanks to both reddog and Dr. Imad

[Deznium]

One more thing I forgot to mention was that my axis (my plot in the front panel) doesn't change at all. X-axis displays 0 and 1 sample values only and at times 0 to 9 samples.
What if I want to display time on the x-axis? is that possible? what am I doing wrong here?
thanks

[Dr._Imad]

just looking at the diagram, change the less than to greater than or equal


you are setting samples per read: 200 at 1000 Hz, you will get 5 updates per second, too quick for my eyes to see it plotted. set it may be to 500 or so ( twice per second)

also if you want to see data appended on the plot, use waveform chart instead


Hope it works