Max sampling rates in differential sampling

I am rather a novice in terms of DAQ and wonder about the maximum
sampling rate. For the DAQ-cards I use (M-series 6221, E-series 6024)
the max sampling rates are said to be 250 and 200kS/s respectively. I
am aware that all channels share a common A/D converter, and that
sampling several channels concurrently limits the max frequency per
channel to a smaller value. But, what if I use differential sampling?
Does this mean I have a reduced max sampling rate since it uses 2
analog input channels? My guess is that I dont, that it is handled
before A/D conversion, but I cant find the answer anywhere.
Hope you can help!

Hello Sirnell!
You will have the same sampling rate regardless of which connections you make (differential,RSE, NRSE), but with the differential connection you will reduce the amount of channel you can use. With an E-series board with 16 inputs you will only be able to connect 8 signals using the differential connection.
For more information about Field wiring take a peek at this link:
http://zone.ni.com/devzone/conceptd.nsf/webmain/01F147E156A1BE15862568650057DF15
For more information about DAQ (glossary):
http://zone.ni.com/devzone/conceptd.nsf/webmain/45ACC30D4A769A3F862568690061D750
Cheers.
Ashwani S.
Applications Engineer
National Instruments Sweden

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Hey Lukos,
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Hi Rocket 154,
You’ve already had some
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Message Edited by JasTan on 03-24-2008 05:37 AM

Generally, the DASYLab sampling rate to block size ratio should be between 2:1 and 10:1.
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brazil101 wrote:
I'm using Audition to do some final mastering to 16-bit stereo 44100 wav files, in 32 float multi-track sessions.
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Hi Guys,
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Attachments:
Panel.jpg ‏18 KB
Block.jpg ‏15 KB

To be more precise, that's the time take for the below mentioned finite cycle
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working_final.vi ‏547 KB

Hi Mike, Thanks for replying.
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After installing Yosemite I am having problem with Sample Rate settings on my external audio interface. It was working perfectly before the upgrade.
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When the message comes up, "Audio sample rate must match sample rate of source tape (Log and Capture window) what exactly does one have to do to ensure a change to the correct .. ?

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Why cant I control the sample rate?

I am sure there is a simple programming answer to this but I am drawing a blank. I would like to slow down my sample rate in the following block diagram, however changing the sample rate at my Sample Clock seems to have no effect. Any ideas? Thanks in advance for your help
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NIquist wrote:
How about a Timed Loop? It's one of the main structures. You can also just drop the Wait.vi (Timing Palette) in your current loop.
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Hello everybody
I am new in LABVIEW and I have some difficulties with something.
I don t know exactly what is the difference between the sample per channel et the sample to read. I believe knowing that the sample per channel is the size of the buffer which is more big than the sample rate but I don t know what is the sample to read.
I ve tested with different sample per channel and sample to read. Sometimes I have an error and sometimes know and I would like to know why. If you have any example for I understand better, it will be great.
I really need to understand this part for my project
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Romaric GIBERT
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Hi Roro,
As you mentioned, when acquiring continuous samples you can specify the sample buffer size by placing a value at the input "samples per channel" on the timing vi. The "number of samples per channel" input on the read vi which automatically names a control/constant with "samples to read" specifies the number of samples you wish to pull out of the buffer in one go when reading multiple (N) samples. This link may provide a bit more clarification. I have also attached a good example from the NI example finder which you may find useful to explore. I'm assuming you are using the DAQmx driver set so please let me know if this is not the case, but the same principles should apply either way.
This therefore means when sampling at a given rate, you need to ensure you are pulling data out in big enough 'chunks' to prevent the buffer from overflowing (which may well be causing the error you are seeing). Conversely if your sampling rate is slow and your read vi is having to wait for the number of samples to read you specified to be available, it may throw a timeout error. You can avoid this by either increasing your sampling rate, reducing your samples to read or increasing the timeout specified at the read vi input (-1 means it will wait indefinitely).
Let me know if this helps and how you get on.
All the best.
Paul
http://www.paulharris.engineering
Attachments:
Cont Acq&Graph Voltage-Int Clk.vi ‏27 KB

How can I programmatically determine the capabilities of a card under NI-DAQmx (e.g. max sample rate, number of AI/AO/CTR channels, etc.

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Attached is a program I've used in the past to determine number of AI channels. It could be easily modified to check for AO or digital or counter. Also, there is a ton of properties that you have access to (i.e. max sample rate, max/min voltage inputs, etc.) that are accessed as properties of the type of channel, or timing properties, as opposed to properties of the board. Check out the DAQmx C Reference Help (Usually at Start>>All Programs>>National Instruments>>NI-DAQ). Expand the NI-DAQmx C Properties, and look at the List of Channel Properties, and Timing Properties, etc.
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Attachments:
Device_Info.vi ‏25 KB

Max sampling rates in differential sampling

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