Readig a 160Hz frequency using arduino + ADXL335 and Labview

Hi all,

I am developing a vibration measurement tool for my master degree and I would like to ask you few questions,

Currently I am using the ADXL335 accelerometer and an arduino UNO board as a data acquisition tool. Once I read the accelerometer values, I send them to labview using LIFA_Base software to perform the FFT and get the Frequency spectrum in labview.

I attach you few pictures about the Labview program and about what I am getting.

As you can see, I get lot of noise in the frequency spectrum, I have selected 350 samples to be over the double of the measured frequency (160 Hz) and perform the FFT.

According to the ADXL datasheet, capacitors act as a Low pass filter and, for some situations, the have to be replaced for other with a different value. Also I think that maybe I should have to make a small offset or similar.

Any help would be appreciated,

thanks.

Alex.

I’m not that familiar with LabView, but if I’m reading the Time Domain figure correctly, it looks like you’ve collected 350 samples over a period of about 5 seconds which is about 70 samples/second. The Nyquist criteria is that the sampling rate (samples/second) be at least twice the maximum frequency in the signal being sampled. That is, you want (at least) 350 samples/second rather than just 350 samples.

4b80901b85075066712a9d505fab03f297b96711.png

An Arduino Uno is capable of these sorts of sampling rates if snapshots of data are collected and buffered on the Arduino, but I’m not clear how one does this with LabView.