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frequency

Hi all,

I want to build a testing system of measuring vehicle vibration and analyze the vibration comfort,I have a CC430 MCU,usb-rs232,and 3 axis accelerometer,I put accelerometer on my book,and wire the hardware. First i need to biuld this system and then i'll put it to test the vehicle.to build this system,i designed the block program.Acceleration data collected by accelerometer was sent to computer through CC2430 and usb-rs232,I extracted data of the x,y and z axis from the visa read buffer and build each axis an array of data using while loop and shifter register,and wire the array to waveform gragh,after I measure frequency using some vis like frequency measure.vi,  the questionn is the amplitude(acceleration)is zero except when the frequency is less than 0.5hz,while generally vibration frequency of the vehicle and amplitude data I need is between 0.5 and 80hz,i tred many ways but still can't figure it out.I don't know why and how to solve this problem.Can anyone help me?II really need your help. Any help would be greatly appreciated.

Thank you.

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What is the frequency response of the accelerometers? Are you buffering the data at the CC430 end, where you acquire the data? I'm thinking that if you aren't the system's overall response may be too slow. Posting an image is only partially helpful, it is sometimes difficult to determine what is going on a program from just looking at a picture of it.

Putnam
Certified LabVIEW Developer

Senior Test Engineer North Shore Technology, Inc.
Currently using LV 2012-LabVIEW 2018, RT8.5


LabVIEW Champion



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The other main question is how fast is the accelerometers being sampled?  If you need to see up to 80Hz you should sample at least 160Hz.  I would recommend more around 300Hz to 500Hz.


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Thanks for your reply.First I need to make it clear that I've made some mistakes:One is the attachment is not my latest program,it's earlier program,the other is the MCU I use is not CC430.What I use is CC2430.

The banwidth frequency of the accelerometer is 400hz on XY axis and 300hz on Z axis.I am buffering the data at the CC2430 end.I acquire the data on CC2430 MCU.

The accelerometer detects the vibration signal and tansform it to ananlog voltage.Analog voltage has been sent to CC2430 analog input.The analog input has been transfiomed to digital data through A/D on the CC2430 and been sent to PC.

The latest program has been attached.

 

 

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The problem still remains.

As far as I kow,there are some ways to for waveform gragh.One of them is to form an array and wire the array to waveform gragh.In this situation,The x axis of the waveform gragh is not based on time.It collects the dots of numbers to form the gragh.So when I want to have frequecy analyze of this waveform.then what the frequency measure is based on. Is it right that the time can be self-set?Sending data to PC requires time.Frequency of acception can not archieve frequency of 80hz.

Is there some way I can get frequency I need?

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You need to somehow give the FFT and PSD functions your sample rate.  What is you sample rate?


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