Multifunction DAQ

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Message 1 of 6
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Re: What is the unit kS/s stand for?

wtawacko wrote in <5065000000080000002B230000-
993342863000@exchange.ni.com>:

>
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kiloSamples per second

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Harry
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Harry J. Decker Mechanical Engineer Voice:(216) 433-3964
US Army Vehicle Technology Center Fax:(216) 433-3954
NASA Lewis Research Center, Cleveland Ohio 44135
Harry.J.Decker@lerc.nasa.gov
Message 2 of 6
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Re: What is the unit kS/s stand for?

Harry is right kS/s stands for kilosamples per second. When you are looking to see how fast you can acquire data the board can take X kilosamples per second. If you would like to know how fast you can get a reading from every channel then you take the kS/s number and divide by the number of channels you wish to scan. This will tell you how many samples you can get for EACH channel per second.
Message 3 of 6
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Re: What is the unit kS/s stand for?

What is this unit of kS / s?
I'm not buying your answer. Because you can write kHz. And as you can see, there is something else.

Message 4 of 6
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Re: What is the unit kS/s stand for?

I first want to highlight that it has been 21 years since the last reply.  In posts old enough to drink, you might get more activity if you create a new thread for your question.

But I'd also like to say why kHz is not appropriate for the sample rate of a DAQ card.  If I say it can sample at 1kHz should I assume it can read 1,000 samples in one second?  Sure.  But what if my DAQ task has 10 channels in it.  Can it do 1,000 samples on each of the 10 channels in 1 second?  Or can it only do 100 samples on each of the 10 samples in 1 second?  The DAQ card itself will typically have a device that can read analog inputs and digitize them.  It will also have a Mux device that can switch the input to the ADC (analog to digital converter).  This way you don't need to have 10 ADCs for a 10 input card, you just need one, and then have the Mux switch which one it can read at one time.  Few DAQ cards are labeled as simultaneous sampling.  But if they are then you should be able to do the full rate, on all inputs at the same time.  If it isn't then you can only perform the maximum rate, when there is one input you are reading.  If you are reading two inputs, the maximum will be half the rate.  So if NI labeled the DAQ cards as 1kHz sampling rate, there could be confusion on what that means.  1 kS/s might also make some confused, but it is different enough that someone may realize it isn't the same as 1kHz.  I've sometimes seen it as 1 kS/s/channel.

Additionally there is a ghosting problem, and switching the mux with unmatching impedance may have the last reading the mux had, be ghosted into the next reading.  As a result your maximum sample rate in the real world may also be much lower.

Message 5 of 6
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Re: What is the unit kS/s stand for?

This answer closes and exhausts the topic.
Thank you.

Message 6 of 6
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