continuous acquisition

[matomato]

HI everyone,

I am a newer in using Labview. I have a NI 9207 module and a DAQmx 9.2.2.  I want to acquire, visualize  and save data from 8 channels.

I would like to write a program that does these taskes and then put the program in a touch panel scereen.

Anyway, I have seen that the example Cont Acq 0.2mA current found in the list of labview examples works well with a single channel, but I would like to do the same with the other 7 channels. So I tried to modify the example for two channels but it does not work.

I have attached the VI.

Someone can help me?

Thanks very much

[Dennis_Knutson]

You have a very common mistake. Use a single task and define multiple channels for it. Click on the physical channel control and select ' Browse'.

[matomato]

Thanks very much Dennis,

I am a newer on labview. 

In this way it is possible to see what happens to different channels simultaneously.

How is it possible to save tha data as a txt. or .xls file?

Regards

matomato

[KRAZE4LV]

I have modified your VI with 8 channel acquision.

The data file is stored in excel.

As I have chosen the channels according to the PXI I am using, you should the choose the channels  by browsing on your PXI/PCI.

It will ask for excel file saving path and name. You can choose the path and file name. The data file will be stored with actual date, time etc.

You can study http://zone.ni.com/devzone/cda/tut/p/id/3116 for learning more about DAQ.

Hope this helps.

Thx

KRAZE4LV

pay me by clicking a kudo !!!!!!

[KRAZE4LV]

Some more study material!

This one has information about programming with NI DAQmx including building Analog Output or Analog Input VI: Getting Started with NI-DAQmx: Getting Started with NI-DAQmx Programming in LabVIEW

This one will be most helpful to get your started with all the DAQmx functions:  Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications

Thx

KRAZE4LV

Pay me by clicking a Kudo! !!

[matomato]

Thanks very much KRAZE4VL...

but now I have another big problem.

I want to use your version of VI to acquire a sinewave from an external signal generator. A sinewave generated by the generator goes to an oscilloscope and to the NI-DAQ. At the oscilloscope I see a very clear sinewave while running the VI I see a kind of square wave different from what I want to see. My idea is that I have sampling problems or I missed some points in the channel configuration.

The procedure used to configure the channel is the following: NI-DAQmx -->Devices and Interface --> NI 9207 (DSUB) cDAQ --> Create a Task --> Acquire Signals--> Analoug inputs ->Voltage--> ai0.

At this point I have fixed the following parameters:

- Signal input range: -10 to 10 Volts

- Terminal configuration: differential

- Acquisition mode: continuous samples

- Sample to read: 100

- Rate (Hz) 1000

- Device: High Resolution

 I didn't touch the parameters under Triggering, Advanced Timing and Logging.

When I push the Run button,  I can't see a clear sinewave on the top of the page and the same happens when I change the parameters to 10 samples at 100 rate or using other values. The signal has always a strange shape different from a sinewave and this is what I don't understand (??). I think that I should see a clear sinewave, isn'it??

Anyway, I save this configuration and try to acquire signal from the generator. What I see is always a square wave while I am 100% sure the signal generated is a sinusoidal wave (from the oscilloscope)!!!!

In the doc. file that I have attached there are three examples of what I acquire by changing the frequency of the generated sinewave.

Surely, there are sampling mistakes but I am not able to understand where and what is wrong!!!

Thanks.

matomato

[Dennis_Knutson]

The specs say the max sample rate is 500S/s so if you are setting it to 1000, you must be getting an error someplace and ignoring it. With 3 channels, your max is 500/3. In high resolution mode, the conversion time is much slower.

Lesson learned - read the manual.