# Multifunction DAQ

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## can a DAQ card Read/Write mode change speed reach 200K

HI,man,

I  have a project needs to test two points,  I name them point A and point B, at the First time, I should give point A 5V DC input, and test point B's inductive output voltage, sencodly, give point B 5V DC input, and test point A's inductive output voltage, it means, two analog ports need to read and write mode exchange, and the test speed must be 100Kb, if I have a 200Kb DAQ card, can the read write mode change speed reach 100Kb for one analog port ? or, please give your suggest for my this kind of situation, thanks.

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Accepted by topic author API

## Re: can a DAQ card Read/Write mode change speed reach 200K

Hi API,

I see you are trying to measure voltages using one channel at a time on a DAQ card.

Unfortunately you can't change inputs to outputs or vice versa on a DAQ card, they are static.

What I recommend is either using a switch such as this: http://sine.ni.com/nips/cds/view/p/lang/en/nid/207130 in which you will need a PXIe chassis.

Or, having four channels, two inputs and two outputs and trying to measure it that way. You should have the speed necessary as well.

If you have any further questions I would be happy to answer them.

Thanks alot,

Message Edited by Owen.S on 09-24-2009 09:57 AM
Owen.S
Applications Engineer
National Instruments
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## 回复： Re: can a DAQ card Read/Write mode change speed reach 200K

Oh Owen.S,

Yup, your suggestion 2 is my better way, thank you. and I have additional concern, depends on my measurement speed, does 250Kb card match? since I believe I should write AO 0V or 5V very quickly(100Kb), and, if I write AO is 0V, how many that channal AO resistance ?

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## Re: can a DAQ card Read/Write mode change speed reach 200K

Hi API,

What DAQ device are you using? Is it NI hardware?

To find out the output resistance you can search on www.ni.com for your device and go to the specification. Hopefully it will tell you everything you need to know there.

Thanks,

Owen.S
Applications Engineer
National Instruments
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## 回复： Re: can a DAQ card Read/Write mode change speed reach 200K

YES, that is NI device, I would like to use PCI-6221, How about this card ? thanks.
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## Re: 回复： Re: can a DAQ card Read/Write mode change speed reach 200K

Hi API,

This card should work fine, the output impedance is 0.2Ω and if your card reads at 250KS/s then writing at 100KS/s on 2 channels will hopefully work too.

Is this okay? If you have any more questions I would be happy to answer them.

Thanks again,

Owen.S
Applications Engineer
National Instruments
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