im acquiring input signal using usb 6009

[Sumithra_Nagappan]

 Im acquirng a dc signal in the analog input ports (RSE),an input volt of 1.9 V is read at the input port(ai0) when i use an multimeter to read the value and at the same time i have used an indicator to display the data read in the input port in my coding,the indicator displays 2.5,sometimes 4V..if any body could help me this please reply me..

 i have another doubt too, i read an document in which they mentioned while using RSE mode the positive end of the source should be connected to the analog input port and the negative end to the ground in the daq..but her im using an dc signal i dont how to connect and what to do..

[lfelias · Accepted solution]

Good morning Sumithra,

I don´t know what could be happening; however, this could be a wiring issue.

First of all, if you are reading this signal I will recommend you to wire the Analog GND with your Digital GND. Also you might need to wire the signal ground to it.

Another thing you might be able to do is to measure in a differential mode, you will be able to connect your NI 6009 like the multimeter.

Here is a tutorial that might be useful for you: http://zone.ni.com/devzone/cda/tut/p/id/3344

Also here are some KBs talking about what you are concerned about. Take a quick look to see if something of this could help.

http://digital.ni.com/public.nsf/allkb/95CC0CB11D7DF3D18625712E000C4ABD

http://digital.ni.com/public.nsf/allkb/C7C4AB4BD256EF0386257013001650E7?OpenDocument

http://digital.ni.com/public.nsf/allkb/C7E181E51E4299FC862570A700604141

Finally, always remember to use Op Amp in the follower configuration to avoid damage your 6009.

I wish you success!!

[Sumithra_Nagappan]

Thank you ur valuable  information..By the By I got the solution for this as soon as i posted this thread,thats why didnt check the forum..Anyway thanks for response