A heart pulse is an ac signal of low amplitude and low frequency.
We need to collect some info on the signal.
My heart beats at 60-65 beats at rest.
When I exercise it rises to 130.
When I exercise flat out it rises to 180.
The pulse rate of world class athletes is as low as 38 and as high as 220.
The amplitude being low we will have to amplify the signal.
Since there will be other electrical signals in our body we will have to reject those.
One source of noise is the mains 50Hz.
IF we try to filter out the mains noise we will also end up destroying signals from people with low heart rates.
What should we do to overcome this problem?
Acquiring the electrical activity of the heart sounds cool!
I think this will all start with the acquisition of the electrical signal of the heart. so here are some of the points which may help you to get started.
As already a lot of work has been done in ECG, so what kind of probes or lead system do you want to use to acquire the ECG signal.
What are the signal voltage ranges (weakest and strongest) of ECG signals acquired from the body?
What are the frequency components of the ECG signal?
Morphology of ECG Waveform.
Let’s start with knowing the ECG signal and this will help you to move towards the development technical requirements of Signal Acquisition, Signal Conditioning, Digitization, Filtering, and storing the data.
Sir @jtd I just want to know that
1.how traditional ECG machine collect data from our body
2.Which types of filter they used to cancel out the noise
3.Please tell me some authentic sources where I can study about ECG signals and ECG machines.
By electrical contact. An electrode - corrosion resistant metal contact is fixed to the skin with suction cups. A conductive gel is applied to the contacts to improve contact.
You will need a notch filter to filter out hum and a bandpass filter to allow the frequency of interest to pass through. Instead of a band pass you can use a high pass and low pass filter.
Several DIY ECG projects on the net.
Since the body is floating electrically one requires differential amplifiers to amplify the signal. Also the signal of interest will be strong around the heart and weaker on other areas of our body. However noise caused by mains signal and other electrical pulses in the body will be stronger on the other parts. Hence we use multiple electrodes to cancel the common signals that are existing on other parts of our body as well as near the heart. The difference of all these signals is our heart beat.
Additionally we need to have well isolated supply, ideally battery powered, to prevent any leakage triggering a cardiac malfunction.
There are ready boards available using ICs having all the filters and amplifiers integrated that have simplified the construction.