are there any possibilities that Labview can cause low frequency spikes on captured data?

[AnalogKid2DigitalMan]

As Mr. Lynn suggested, use a scope if handy. Also remember, the environment may be noisy in the frequencies above what you can hear.

-AK2DM

[Robbob]

There are some great bits of advice here, but I will throw in my 2 cents...

I think the others' suggestion for using a scope is your best bet right now, this will isolate the acquisition hardware and at a higher frequency so we can see the actual noise profile. Based on what has been found so far...I think your sensor or wiring is suspect.

It appears the noise is at a higher frequency than your actual sample rate...so if we were to put a low-pass filter in with the correct cutoff frequency, we would be able to isolate the signal from your sensor and the ADC/software. Also, we can test cable noise as well by putting the sensor close to the ADC or close to the actual sensor. If the noise is present when the filter is near the sensor, but not when it is near the ADC, then we can say the wires are picking up noise. Have you tried a simple twisted pair for your cables as well?

Also, there are several questions to be asked...

What device are you using for acquisition?

Is it differential or single ended?

Are any other instruments connected and are you sharing a ground with anything else?

What is the specced range of the device? Some devices have a minimum/max range, and if you measure  something outside of that, you get odd results.

Message Edited by Robbob on 01-25-2010 11:56 AM