adxl206 sample rate quesiton

jainchen2 on Mar 6, 2017

Hi,

I use ADC to read ADXL206 XOUT YOUT voltage with Cx Cy set as 1uF. On page 10 of the datasheet, there is a formula f(-3dB)=1/(2pi*32K*C), I calculate f(-3dB)=5Hz when C is 1uF . In the firmware I set ADC sampling rate as 10Ksps(sample per second). Is it good for noise immunization? I don’t understand the rms noise formula on page 10 of ADXL206 datasheet.

Thanks, Jian Chen

0 NevadaMark

on Mar 6, 2017 11:18 PM
Thank you for your post! Based on what we have experienced and understand about this sensor's behaviors, 10kSPS should work well for you.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 NevadaMark

on Mar 6, 2017 11:23 PM
With respect to the total noise equation, I assume that you are referring to the equation that is yellow highlighted in the embedded graphic (see below). Assuming that is correct, you would use the same example, only you would use 5, instead of 100. Does that help?

rms Noise = 110ug/sqrt(Hz) x sqrt(5x1.6) = 0.3mg (rms)
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 jainchen2 on Mar 8, 2017 5:22 AM

I saw a sentence on page10 of datasheet right hand side: “The output of ADXL206 has a typical bandwidth of 2.5kHz... The analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimize aliasing."

So the sampling frequency should be at least 5kHz. In my case, 10kHz should be fine.

Is it correct?
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 NevadaMark

on Mar 8, 2017 6:33 AM
Yes, that is correct.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel