As already indicated, we are hard pressed to imagine precisely what circuit you have in mind without a schematic.I couldn't understand this circuit's operating.
Could you help me about this circuit details?
By carefully adjusting the pressure of the device on the index finger (or any finger with a good pulse), it should sense a change with each beat.The absorbance of oxyhemoglobin and deoxyhemoglobin is the same (isosbestic point) for the wavelengths of 590 and 805 nm
I'm sorry I couldn't understand this sentence;Are you referring to the function of C5? Remember, you are looking at the change in intensity and want to block DC. The rate of change for the pulse edge will be higher than the average pulse frequency.
As you said:"The width of the pulse is much narrower than one-half of the distance between pulses" Can we calculate the frequency of the pulse?I have read your document but I couldn't find the frequency of the pulse. How can i determine the frequency of the pulse which will be processed?You calculated a high-pass cutoff of 7.2 Hz (I have not double-checked that calculation). Since heart rate is about 1 to 2 Hz max (not 0.5 Hz, which equals a pulse rate of 30), I interpreted you were asking how that low a frequency could get through the high pass filter.
If you look at an actual pulse pattern, such as here: http://www.cse.iitb.ac.in/~ajjoshi/modernPulse.pdf
you will see that a typical pulse is not a sine wave. The width of the pulse is much narrower than one-half of the distance between pulses. Also, the pulse is not shaped like a sine wave. Thus, there are many frequencies in an arterial pulse that are higher than the cut-off you calculated.
As an interesting physiologic experiment, does your device work on the thumb and other fingers?
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