daq reading voltage

[fadetoblack]

Hello

I´m using a NI USB-6211 to acquire voltage. I´m using voltage probes with atenuation in order to measure values above the limit of +-10V.

The problem is:

- The value that I read in Labview (RSE, continuous samples... just a straightforward reading) is not sensitive to atenuation

This means that when I´m reading 8V without atenuation (confirmed with voltmeter at the pins of the daq board) I'm reading 8V -> Correct

When I use an atenuation of 10x and reading 0.8V at the pins of the daq board with the voltmeter, I still read 8V in Labview -> Incorrect

Hope that my question is understandable

Thanks in advance

[Coq_Rouge]

What kind of probes are you using. If you are using scope probes your setting will not work because scop probes are made for 1 Mohm input.

A scope probe look like this

The RP is a 9Mohm resistor. The ratio is equal to Vin*(Rin/(Rp+Rin)=Vin(1/(1+10). Your daq board has a Rin equal to to 10 Gohm. So the ratio will be in Mohm=10000/(10000+1)

Message Edited by Coq rouge on 05-25-2009 03:35 PM

[Coq_Rouge]

Sorry made an error in my last equation. The correct ratio are 10000(10000+9)

[fadetoblack · Accepted solution]

Hello

Thanks for the help. You are absolutely right!!

I´m going to modify the input circut in order to include the 1Mohm resistor and then pass the voltage value to the daq board.

Thanks again

[Antoine2g]

Greetings

I am using LabVIEW version 7.1 with a National Instruments PCI-6713 12bit.

I am not at all familiar with the LabVIEW program.

Can anybody please provide a (simple) voltage data acquisition software?

It will be used to obtain data from some brand new Kistler pressure sensors for a Research Project.

One or two channel does not matter - if one I will use one pressure sensor at a time.

Grateful for any assistance; ofcourse recognition will be possible in any acknowledgements and/or publications if desired...

[Coq_Rouge]

As a starter you can go to help in the toolbar and then select find examples. Serach for "continuous acq" I think the example "Cont Acq&Graph Voltage-Int Clk" should be usefull. All examples that show a MX icon is correct for you

[Dennis_Knutson]

Your question has nothing to do with the original post and you should really have started a new thread.

You can find a lot of examples just by going to Help>Find Examples. You will of course, first have to find a different DAQ board since yours is not capable of acquiring a signal. Did you ever look at the specs?