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Standalone solution with NI 9205 and cDAQ9171

Hi Forum,

 

i am working on a project for what i need 10 AI with high sampling rate (min. 150khz). The device should be standalone and used in remote locations connected to a mini itx board and recording data over some hours. 

I was thinking to use a cDAQ9171 with USB connection combined with the NI9205 Module.  I would like to use the intel Desktop Board DN2800MT run windows or linux (if there is a driver?), because its low power consumption. 

The first application should be just streaming the data to the hard drive or record data when a event happened. 

 

Anyone has experience with this combination?  

 

Thanks,

Martin 

 

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ok i will not get this high sampling rate with the NI  9205 as its 250ks/s / 10 channels, but can i expect 100ks/s with the PCIe 6351 or can i change the sampling rate within the channels (4 faster, 4 slower)?

 

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The 6351 gives you 1 MHz / N Channels (when N>1).  So at 10 channels you would indeed be able to sample each at 100 kHz (keep in mind it's MUXed so there is an offset between channels).  There is a USB variant of this as well.

 

You can't run the channels at unique sample rates per se... but you could configure a task with a scan order like this:

 

fast channels are {A, B, C, D}

slow channels are {1, 2, 3, 4}

 

A B C D 1 A B C D 2 A B C D 3 A B C D 4 ...

clocked @ 1 MHz

 

It would give 200 kHz for A, B, C, and D while giving 50 kHz for 1, 2, 3, and 4.  It's kind of a niche use case but might help you out.

 

 

The 9220 would be an alternative to the 9205 if you prefer the C Series form-factor.  It gives 100 kHz per channel with 16 channels of input.  It is not multiplexed so does not have the same channel-to-channel delay issue.  All of the channels sample together off of the same clock so they must also run at the same rate.

 

 

Unless you have a compelling reason to use Linux I'd suggest running Windows if possible as it has better support from NI.  Looking at NI's support for Linux for both PCI/PXI and Portable devices, your best Linux option is probably the PCI / PCIe-6251 which will perform similarly to the 6351.

 

There is the RT option as well that you might consider (cRIO / PXI seems excessive to me for this application and the standalone cDAQ chassis are quite expensive).  There's a pretty substantial software cost though.

 

 

 

Best Regards,

John Passiak
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Hi John,

 

thank you for your answer. Yes i was considering using the NI 9220 the sampling rate should  fine for me, also for a standalone application the form is perfect. 

But I would like to set triggers on special events, so as i see the NI 9220 doesnt support analog triggering but i could set tresholds with Labview and then get the events with high sampling rate, otherwise i would like to downsample the data. 

I will work with Windows as you said the support is better, RT is not important for my application.  

But using the USB device i was wondering as i  can really get 100Ks/s on 10 channels streaming?

 

Thanks 

Martin

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Hi Martin,

 

I suppose you are talking about the NI USB-6351 now. As you can see in the specifications the sample rate of 100kS/s is possible with the USB device.

 

Regards,

 

Anna

Anna Vogl
Certified LabVIEW Developer
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Hi, 

 

i will take the NI 9220 100S/s/ch sound great combine with a NI cDAQ9171 1 slot USB.

I am planning the software in lab view and I would like to trigger (pre and post trigger) on special events (peaks, sags...) then get highest sampling rate, otherwise I would like to down sample(average)  my measurements. 

Does someone has experience with this setup would be nice to discuss the ideas. 

Thanks
Martin

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mmmh, that sounds not so trivial. You have to set the trigger and the sampling rate before startig the task. If you set your trigger to a certain value, acquisition will start only there and not before. Maybe someone else has an idea how to implement that. But I don't see a way there.

Can't you use the highest sampling rate all the time?

 

Anna

Anna Vogl
Certified LabVIEW Developer
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HI Ann,

 

i watched the rigger examples on the NI webpage, yes u have to set sampling rate at the beginning, but i was thinking about just to callculate the everage of 100 values or the RMS while its checked for the threshold and write this down to a file. 

I would not like to sample all the time with 100kS/s on all channels because the DAQ should run over 6h and would be a lot of data to evaluate.

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HI Martin,

 

have you looked into the example of daqmx signal acquisition with events? maybe thats the way you can implement that. If not you would have to poll the value of the signal and process it in 2 different cases. Then you would still have the maximum sample rate but could log only the average at the points needed.

 

Anna

Anna Vogl
Certified LabVIEW Developer
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Hi Anna,

 

yes i have modified a example with events. I can set triggers on each channel (window) every time a event happend i will get the full data with pre and post trigger. On the other side i will calculate the average RMS and other values as well as i use ownsampling (average) to get less data. I still dont have my Hardware but i tried it with the simulated device and looks fine, hopefully i get the Hardware this week so i could see if its really works. 

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