Rif.: Eliminate noise from USB 6009

[ciofi94]

Hi, I'm a student and I'm having some problems with my USB6009. I need to measure the voltage from a battery and I'm trying with Labview and the DAQassistant but I have too much noise. I've attached the data that I have collected where there's nearly 0.02 mV of noise. How can I eliminate that noise?

I'm sorry for my english level.

Thank you,

Giovanni

[natasftw]

Are you using a differential measurement?  If so, the noise should be on both lines so when you perform the subtract the noise is cancelled out.

Where is the noise coming from?  Consider your input is 14-bit in differential.  1/(2^14) = 0.000061  That's a resolution of 0.06mV.  If you're concerned about 0.02mV, your device is useless to you.  Assuming zero noise and a perfect signal, your quantization error can still be up to 0.03mV.

[ciofi94]

I'm sorry, my error is about 0.02V not mV. And I'm using RSE measurement, I'll try with differential measurement,

Thank you

[natasftw]

20mV is something you can work with.  Did the differential measurement help?

[ciofi94]

I'm using a temperature sensor lm35dz and I'm able only to measure refering to ground by using a 220 ohm resistor between the analog input and the ground. The sensor has three pins: 5V power, ground and the output signal that I read. How can I use that sensor in a differential mode?

[FatBoyMonchi]

You can power it with an external power supply and use the com and output wires to acquire the signal.

Bye

FBM

[ciofi94]

That seems I'll use use RSE but I need differential measurement, I don't know how to do that.

Thanks

[FatBoyMonchi]

Look at page 9 of the manual: http://www.ni.com/pdf/manuals/371303m.pdf

Here you can see that if you want to use the channel 0 as differential, you have to put the positive signal on the pin 2 (AI 0+) and the negative one on the pin 3 (AI 0-).

Bye 

FBM