FFT resolution

[Bildavid]

Hey guys,

i was looking for FFT  function that has resolution input as an option to select.(200Hz)

The resolution (Hz) in an FFT result is  R = Fs / N, where Fs is the sample rate (samples / sec) and N is the number of samples in the block.  so i put an indicator to manually select the sampling frequency, and an indicator to manually set the number of samples, then divide them and get the resolution.

m confused i just need to select the resolution of the signal to be fed to the FFT function...

hope i made it clear.

any suggestions guys ?

[GerdW]

Hi Bill,

your Fs is given by your signal acquisition routine, N is given by the blocksize of data you fed into the FFT routine. Either change your DAQ to use other Fs or collect data to change the blocksize N.

No other inputs to a FFT are required...

[johnsold]

Biil David,

If you need N to be larger than the amount of data you have available, pad the data with zeros to the desired length.

Lynn

[Bildavid]

DAQ is not my case . m jusr reading from a serial port . the attached image shows that i am doing  BUTTERWORTH filter with sampling frequency that i can adjust, as well as higher and lower cutoff frequency.

after filtering the ECG signal ,i wired my signal to a peak detect function found in the biomedical toolkit, to display peaks and graph it .

i just need to do a FFT to make peaks look clear. so i thought to determine the resolution of the signal to be fed to some function then feed it to FFT function...

hope m not misunderstanding.

regards.

[Bildavid]

sorry forgot to attach the image

[GerdW]

Hi Bill,

there's no picture...

Even when you don't do the DAQ on your own there has to be some DAQ. You have to know the sampling frequency of your signal...

[Bildavid]

HI GerdW

the sampling frequency of the ECG signal should be at least 500Hz, but i decided to control it manually , i can put it 1000 for some purposes... and i am not using DAQ i am reading from a serial port.

thank you .

[Dennis_Knutson]

You don't understand the basics. You absolutely do have a DAQ. You already said you did. The A/D is part of your micro. You set the sample rate for that and if you don't know it, find the person that wrote the micro code for you.

[Bildavid]

Dear Dennis_Knutson

with all my respect dear friend but i do not have time to convince you sir that i wrote the code or someone else did . 

anyway here i attached you the code . you can see that i only selected the baude rate (signaling rate , speed ) to be 19200.

where is the sampling rate here ?

Regards.

[Bildavid]

Dear Dennis_Knutson

with all my respect dear friend but i do not have time to convince you sir that i wrote the code or someone else did . 

anyway here i attached you the code . you can see that i only selected the baude rate (signaling rate , speed ) to be 19200.

where is the sampling rate here ?

Regards.