Noise problem with mV analog signal

[juliasmith]

Hello everyone,
This is the first time I'm reading an analog signal with LabView, so I'm sorry for how little knowledge I have.
I am trying to read an analog voltage signal between 20mV and 200mV (proportional to a temperature 1mV=1 degree Celsius and given out by a thermometer) with a NI DAQ Device(NI USB 6009)(I have connected my signal to the Al0 +/- inputs). I use LabView to obtain the signal from the DAQ Device. My problem is, that my signal is very noisy. I get noise on the scale of 10 mV. If I average this noisy signal over 2s I get a smooth temperature curve without any noise. My question is whether there is anything I can do in order to reduce this noise in the first place?
I have googled this problem extensively but couldn't find a solution myself.
I would be really thankful for suggestions!
Julia

[crossrulz]

Make sure you are not using the maximum scale, which is the default.  The minimum range for the 6009 is -1V to +1V.  So set the range to that.

[juliasmith]

Thanks a lot! Now my noise has a range of 5 degree Celsius instead of 10. Does that mean that I just don't have the right DAQ device for measuring low voltage signals with higher accuracy?

[crossrulz · Accepted solution]

There are DAQ boards that will have a lower range.  I try to get a DAQ with a range that makes sense for your measurement.  If you are measuring a 75mV max signal, try to find a DAQ that has a range for 100mV.  But that is just a rule of thumb.

There are other possible tricks to lower your noise level, depending on how your hardware is set up.  But that would take a lot of information to diagnose.

[juliasmith]

Thanks a lot for your help! I'll get a different DAQ device, that better suits my requirements.