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EVAL-ADXL001

Question asked by Danh on Nov 6, 2015
Latest reply on Jan 5, 2016 by NevadaMark

Hello everyone,

 

I have built a testing setup that uses EVAL-ADXL001 as a calibration for the acceleration applied.  A general view of the setup is shown in the figure below.   Basically it is constructed of a speaker that serves as a shaker.  A plastic fixture (white plate and holder in the picture) that holds a metal (brown) box is fixed to the speaker.  The metal box contains the EVAL-ADXL001 with input BNC for powering the accelerometer and for viewing the signal on the scope.

 

Displaying IMG_1295.JPG

The acceleration I would like to be able to measure are around 0.5-1G.  The problem is that the noise level is still relatively high.  I am using a 22nf for C2 and 300Ohm for R1 in order to remove high frequencies noise.  In addition I am using batteries to power the device (They are shown in the picture above).

 

The results below are what I measure.  The signal is for sin vibration at 50Hz. The PTP amplitude is 50mV.  With 4.8V powering the device this is about 2G.  The noise PTP is about 20mV.

 

Displaying IMG_1300.JPG

If I use averaging, that is offered by the scope, the noise is reduced as shown in the figure below.

 

Displaying IMG_1296.JPG

Here the PTP is 5mV, that is about 0.2G.  This is nice but I rather not use average to get the results I need.

 

Any thoughts how to reduce the noise are welcomed!

 

Maybe placing the batteries in a faraday cage.  I saw power sources with noise as low as 4uV. would this help?

 

Thank you

Dan

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