Determining the Cutoff Frequency of a MEMS Accelerometerby rahlk Tags: accelerometer, cutoff frequency, low pass filter 

#1
Feb413, 09:29 AM

P: 4

Greetings Forum,
I just bought an Invensense MPU6050, I need to design an LPF to filter the noise. How do I analyse the signal and how do I determine the frequency beyond which the signal is altered by noise. Thanks in advance for your help. Cheers 



#2
Feb413, 07:18 PM

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P: 39,638





#3
Feb413, 09:16 PM

P: 4

I will be using it to estimate the tilt angle. I am going to interface it to a microcontroller. In fact, I need to submit a term paper on this, so I'll have to describe my filter quite clearly.
The Datasheet  http://www.cdiweb.com/datasheets/inv...MPU6000A.pdf 



#4
Feb413, 09:48 PM

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P: 39,638

Determining the Cutoff Frequency of a MEMS AccelerometerSo tell us what you see in the datasheet. Are there any app notes? What kind of noise do you expect in your data acquisition setup? What order and polynomial do you think you will want to use in your project, and *why*? 



#5
Feb413, 11:08 PM

P: 4

Well, accelerometer is subject to several sources of high frequency noise, including thermal, electrical and mechanical vibrations. I thought of developing a simple first order, singlepole infinite impulse response LPF, given by,
y(n) = α.y(n1) + (1α).x(n), where, x(n) = current accelerometer reading, y(n) = current estimate; y(n1) = previous estimate. My issue is with determination of alpha. If sampling frequency is Fs then, α = [itex]\frac{\tau Fs}{1+\tau Fs}[/itex]. and, [itex]\tau[/itex] = [itex]\frac{1}{2\pi Fc}[/itex]. Once I determine Fc, I can justify my choice of α. Now, If the device were analog in nature, I could have designed an RC LPF, got the state equations, taken a laplace transform and applied Bilinear Z Transform to get the digital equivalent. But this device gives acceleration in digital format, a 16 bit number. I need to be able to somehow use Fourier analysis or some such technique to work on this digital data directly. I would be delighted to get some help on clarifying this conundrum. 



#6
Feb513, 04:01 PM

P: 4

From your initial post: 


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