Selection for DAQ card

[Sacl]

Hi:

  I am trying to select a DAQ card for my research project.  My project is like: First probe and amplify a electrical current from a electrolyte solution by using a patch-clamp amplifier, then pass the signal to DAQ card, then do some feedback control to the amplifier.  I saw some people use PCI6070E-1 because they said:1.It supports analog output waveform generation with an analog  input trigger 2. It  has a fast read speed 3. It can do the feedback control.  I am wondering if PCI-6251E can do the same thing?  Since I really have no knowledge on these products, so I really dont know how to choose among all these DAQ products.  Thank you very much.

[gwd]

Superficially 6251 is newer and has better specs for most things. By the way, you have the part number slightly wrong as 6251 is M series which means it is newer technology (which is probably the reason it's cheaper). The 6251 is 16 bits vs 12 which gives potentially better resolution and which may not be achievable in a noisy measurement.

Seems to me you have a choice between doing a really careful comparison of the specs and doing the safe, easy thing and buying a proven solution.

[Sacl]

Thanks for your suggestions. I saw from one previous paper that use PCI-6070E to do the experiement that's similar to my future project.  And I am considering the PCI-6251M simply because it has higher resolution (16-bit) like you suggested!     

  So I would like to make sure that: Is there any specific features, like analog input/output or others, that PCI-6070E has, but PCI-6251M does NOT?    Also, how did people choose from all these DAQ products, like whether choose PXI or PCI or ISA, or R series or.....?  Thank you very much.

[Jesse_O]

Hello,

I can try to provide a little more information.  First, the 6251 does support starting an anlog output based on an analog input trigger.  To do this, you can connect the signal you want to trigger off of to the APFI0 line on a M Series.  This routes to the trigger circuitry which can trigger the analog output task. 

One difference between the E Series and M Series is that the E Series can perform bipolar or  unipolar inputs (i.e. +/- 10V vs. 0-10V input range).  This unipolar inputs is not an option for M Series.  You always need to specify +/- 10 V even if you read in a signal between 0->10V.  The absolute accuracy on the 0.1V scale for the M Series is 52uV versus 163uV for an E Series for an analog input.  The Trigger Circuitry for the M Series is 10 bits, versus 8 bits for an E Series.  Finally, an M Series can have correlated digital outputs on port 0 (clocked off a counter), whereas the E Series is just static output.  You can find the complete specifications document here for the 6251 and here for the 6070.  There is also a more generic difference page here for E Series and M Series.

Now for the different bus technologies.  ISA is an older technology, and most computers do not have slots for this anymore.  The more common bus it the PCI bus.  This is what almost every computer today has.  PXI is similar to PCI, however it has some extra functionality.  You also need to purchase a special chassis to use this type of card.  R Series boards have an FPGA that you target with LabVIEW FPGA but they can perform analog and digital tasks.  R Series can be found in PCI and PXI.

I hope this provides you with a little more information.

Regards,

Jesse O.
Applications Engineering
National Instruments

[Sacl]

Hi:

  Thank you!  I have looked up in the datasheet for both PCI6070E and PCI6251M to understand how you calculate the resolution.    So do you mean that in the unipolar case in PCI6070E, if I specify the analog input range to be 0-->10V, I would get the resoluion of 10/(2^12)=0.0024V, while in the bipolar case of PCI6251M, I can get the resolution of 20/(2^16)=305uv?    And PCI6251M can specify the range to be -10-->+10, -5-->+5, -2-->+2, or others, right?

  Also, I saw from FAQ page that DAQ card can provide a DC offsets for analog output.  Does this mean that I can use PCI6251M to actually prvide a 5VDC to a electrolyte solution??(But this sounds impossible)?   Thank youvery much.

Jason

[Ed W]

Hi Jason,

Your calculations for the resolution of each DAQ device are correct.  Regarding the +5 VDC input to the electrolyte solution, this is definitely possible, unless I’m misunderstanding your question.  These devices are capable of producing outputs of up to 10 V, so I’m not sure why 5 V would be a problem; please post back if you have any further clarifications or questions.

Regards,

Ed W.

Applications Engineer

National Instruments

[Sacl]

Hi:

  Thanks a lot for the suggestions.  So in conclusion, can I just use PCI6251M, as a updated drop-in DAQ card replacement for PCI6070E-1? 

   Also, I would like to know what kind of Labview should I purchase?  I saw from the webites that there're mutiple choices for labview , like Labview basic, Labview windows, Labview full, Labview SignalExpress, or others...    I am wondering how could I choose from all these producs?

  And besides Labview, do I need to buy driver for my PCI6251M , or is it included in the DAQ card?  

Best,

Jason

[Ed W]

Hi Jason,

The PCI-6251 can be used as a drop in replacement to your E Series devices as long as you are using the DAQmx driver.  M Series devices only work with the DAQmx driver – they will not work with Traditional DAQ.  So you’ll want to check into any existing LabVIEW code that you plan on using to make sure that you’re not using the Traditional DAQ driver.  However, if you are using this driver, depending on the complexity of the code, it may still be worth it to upgrade your device and driver to use the M Series/DAQmx configuration.  Just in case, I’ve placed a link to some documentation describing the transition from Traditional DAQ to DAQmx.

Transition from Traditional NI-DAQ to NI-DAQmx in LabVIEW

The DAQmx driver (like the majority of our drivers) is available as a free download. 

For the application software, check out the following link describing the options available for different LabVIEW packages.

Choose The Right Option for You

All of the LabVIEW packages will work with DAQmx and your device, regardless of the driver. 

LabVIEW SignalExpress is a menu driven application used for data acquisition and logging with the DAQmx driver.  If you do not need much more functionality than this, it may be a good choice.  A light edition of the software installs with the DAQmx driver, so you can at least test it out for free.  However, if your programming requirements extend much beyond simple data acquisition/logging, LabVIEW will give you much greater flexibility for all of your programming needs.

I hope this helps.  Post back if you have any further questions. 

Best regards,

Ed W.

Applications Engineer

National Instruments

[Sacl]

Hi:

Thanks a lot.  I just found out that the PCI6251M has analog and digital triggering.   My questions are:  So what do they mean by analog triggering?  Does it mean that I can specify  many criterion values that the machine will be triggered when exceed/below this value?  And does digital triggering means that they only have one value?   And for PCI 6251M, since it said it has analog AND digital triggering, so does it mean that I could choose the triggering mode I want? 

  Since I am trying to replace the PCI6070E with PCI6251M, and because the way it's triggered is critical to my project, I would like to make sure if the PCI6251M can do EVERYTHING PCI6070E-1 does...   Thank you.

Jason

[Ed W]

Hi Jason,

By analog triggering, they mean that you can use the characteristics of an analog signal to trigger the start of an acquisition or generation task.  Like you mentioned, you can vary several parameters of the analog triggering to choose the correct triggering type for your application.  The digital triggering means that you can use a digital signal to as a start trigger or a reference trigger for your tasks.  The following Developer’s Zone tutorial explains these concepts in more depth.

Tips and Techniques in Data Acquisition Triggering - NI-DAQmx

The PCI-6251 should make a great replacement for your PCI-6070E.  Please post back if you have any further questions.

Regards,

Ed W.

Applications Engineer

National Instruments