USB 6211 noise problem

[EEsRULEtheWORLD]

How did you connect the bias resistors when using differential mode?  What values of resistors did you use?

[Bill Wang]

For NRSE model, I used two same resistors from 20k, 40k, 60k, and 80k. One is put between AI and AI GND, and the other one is placed between AI SENSE and AI GND.

For DIFF model. I used a resistor from  20k, 40k, 60k, and 80k, since I use DC. It's placed between (-) input and AI GND.

Among all of these cases, DIFF mode without resistor gave the best result, which is still not acceptable, not much noise. 5mV/200mV

Today I used another Data Acquistion Card system (24 Bit) in our lab to record my data. It has very little noise, 0.1 mV. So I guess the card I'm using (USB 6211) has problem.

What else shoud I do? Should I send it back since we just bought it in April? Thanks for all help from you.

[Bill Wang]

Even the card is 16 bit, I don't think it should generate too much noise compared with 24 bit card. Am I right?

Thanks for you  help!!

[Bill Wang]

any help? please

[EEsRULEtheWORLD · Accepted solution]

Hi, Bill.

The USB-6211 has a range accuracy of 2.69 mV for the maximum voltage range.  Therefore, you should only see a maximum of +/-2.69 mV change from your known input signal.  Since you are experiencing a maximum of +/-200 mV change on your known input signal, it is possible that the device could be damaged, but you should really create a service request and call in to make absolutely sure. 

Before you call in, I would try connecting your analog ouput channel to your analog input channel via a single wire.  Open Test Panels in Measurement and Automation Explorer (MAX) and produce a constant DC voltage on the analog output channel, while reading the voltage signal on the input channel.  You should see a fairly clean constant DC signal on your input channel.  If this is not a constant DC signal and you're still experiencing the same type of error, you should create a service request at ni.com/ask and call 1.866.275.6964 with your service request number.

I hope this helps.