at what data rate should i take values? and how to code for it

I am using arduino matlab along with pulse sensor and I am not satisfied with the output as I dont think I am getting dicrotic curve I have written my current code and output that I am getting and what I am hoping to get. Also will any signal processing technique improve the output. please help.

output obtained

current code:

clear all

close all

clc;

a = arduino();

%%

v=zeros(500,1);

t=seconds(v);

t0=datetime('now');

for c=1:500

v(c) = readVoltage(a,'A0');

t(c)=datetime('now')-t0;

end

%%

plot(1:c,v);

title('Vata');

expected output

Answer 1

[Star Strider]

For cardiovascular data (including EKG) recording, the minimum sampling frequency is generally considered to be 250 Hz, giving a Nyquist frequency of 125 Hz. This will capture all the necessary data, and allow for filtering and other data processing. You can always downsample the data later if you want, however you cannot create data that you did not originally record.

[Amit Kadarmandalgi]

what about using a PPG sensor and also what does it mean by 125 Hz ? should i take like 1250 saamples in 10 seconds? if so how to code that

[Star Strider]

You should take 2500 samples in 10 seconds, or 250 samples/sec.

I do not have an Arduino, so I cannot help you with the coding for it.

[Amit Kadarmandalgi]

I need only matlab coding as I am using matlab as the main software and arduino is just used for data acquisition from sensor

[Star Strider]

I do not have an Arduino, so I cannot write any code for it at all.

I am specifically responding to your question about sampling frequency for cardiovascular signals.

[Madhu Govindarajan]

MATLAB Support for Arduino might not be able to handle that high of a frequency, that was one of the main reasons we used Simulink support as explained in this video for ECG signals - https://www.mathworks.com/videos/how-to-build-a-heart-rate-detector-using-arduino-and-matlab-1520412607264.html

[Star Strider]

@Madhu — Thank you. I wasn’t aware of that video.

[Amit Kadarmandalgi]

but is it the same for PPG sensor?

[Star Strider]

@Amit — Try it.