DAQ USB-6008 Application

[ukmaster]

Hello.

I am thinking to use two DAQ USB-6008  simultaneously with two USB ports on Lab view 8.0.

But, I am not sure if it would work.  Are there anybody who have tried before?

Please let me know if you think it would work.

Thank you.

Choi

[ryan_d]

Hi Choi,

You will be able to use two USB-6008s simultaneously. The theoretical input bandwidth of the USB-6008 is 10k Samples/second. National Instruments USB devices are built to USB 2.0 Full-Speed specification which presents a total bandwidth limit of 12M bits/second. This means you could have 1200 channels of USB-6008 in a USB RAW acquisition. Theoretically, then, you could use 100 USB-6008 devices at once.

Note that there are further limitations in continuous acquisition and streaming of data, and these theoretical rates may not be achieved on every computer system.

Please post back if you have any questions. Have a great day!

[arielmedina61]

Sorry, Ryan D. :

Could you help me with this question?

I have a new question about  usb 6009 daq card.

Is possible use a pseudo "autoranging input"  in its phisical channels?.So,  I will explain about this:

I am measuring a voltage signal that varies from +/- 20 mV to  +/-  20 V. If I configure the input voltage at +/-  20 V, when the input is about 20mV , the resolution is too poor.
Is there any  in daq tool that chooses the best input range according to the signal amplitude?

Thanks

Ariel Medina

[ryan_d]

Hi Ariel,

Please in the future create a new thread when asking a new question. Having a unique question for each thread makes the discussion forums easier to search and more effective for other users.

There is no way to automatically adjust the input voltage range in hardware. However, you can programmatically do this using a DAQmx Channel Node.

1. Right click on the block diagram and select Measurement I/O » NI DAQmx » Channel Node.
   
2. Place the channel node inside of the while loop for your continuous acquisition before the DAQmx Read.vi.
   
3. Expand the channel node and left click on the property and then select Analog Input » Maximum Value.
   
4. Do the same for the minimum value.
   
5. Finally, you need to set up some logic to dynamically change the range based on the input data. In the attached example I do this using a case statement that outputs the appropriate range based on the absolute value of the data.

Attached is an example VI that will dynamically adjust the analog input voltage range. Keep in mind that once a range is set, any value that falls outside of that range will not be acquired correctly and you may encounter DAQmx errors.

Please post back if you have any questions. Have a great day!


Message Edited by ryan_d on 11-06-2007 03:40 PM

[arielmedina61]

Hi, Ryan D.:

Thank you very much for your assistance. I will test this vi and  I will report you how it works.

Sorry , I feel like a dummy, because I don´t know how to create a New thread. When I click it , the navegator lunch to another window

Thanks again.

Regards,

Ariel

[arielmedina61]

Hi Ryan:

Sorry by  delay my reply.

I 've tested this vi and it works ok with my Ni 6009.

Now the following problem I have is a large delay to aquire a lot of samples.
I need to aquire 5000 samples into 3 channel.

Actually, to do this, I use DAQmxRead (Analog, 2D DBL N Chan N Samp. i.e. Analog/multiple Channels/ Mult Samples/2D DBL mode and then I work with math. ( Without your autorange vi)

Thanks,

Ariel

(sorry by my poor english)

[BROhan]

Hi Ariel,

That was quite a long pause between posts! Since this is a new question altogether from your previous post and from the original USB-6008 question, I would suggest to create a new thread (you can do this from the particular board you want to post on and clicking on New Message). I would suggest to look at the Example Finder within LabVIEW. You should take a look at Help->Find Examples->Hardware input and output->DAQmx->Analog Measurements->Voltage. If you have more specific questions, please feel free to create a new thread so that we have a good track of your question.