Pulse oximeter: measurement of pulse and oxygen saturation of arterial blood

I supposed a layout could be made
(current to voltage) >> (filters) >> split into two multiplexed signals >> (100n capacitor) >> (amplifier) >> (ADC)

I am probably wrong, but I wonder why you can't do that. I don't know much about analogue

Very interesting device. And could it be used to measure your heart rate during exercise? Ie. Will this method of measurement (finger clip) not cause a lot of errors when moving the delinquent?

Since one image means more than a thousand words, I attach drawings. The surgery performed for me looks like this:


The operation proposed by a friend, however:


The horizontal axis is the time axis. We see that in the second case, direct filtering of the multiplexed signal causes a complete blurring of the difference between the channels and the inability to recover the information originally contained in them.

When it comes to the use of the device in measuring the pulse of athletes, for this purpose pulse oximeters completely contained in the clip housing are used (the clip itself is the whole device). Thanks to this, when moving the hand, we do not feel the resistance of the cable, and thus the movement of the sensor relative to the finger is smaller, which results in less reading interference.

Thanks for the clarification. It became logical and obvious.
What filter did you use and at what frequency do you cut the band?

at the beginning I would like to congratulate you on the successful project, I have a question about the photodiode you used, namely I suspect that there is no equal sensitivity for 2 wavelength, did you compile it somehow?

Can the input amplifier be replaced e.g. with OP07 or something else cheaper? and as 2 amplifier already use something like lm358? I mean the measurement of the pulse itself once wanted to play with it but I came back only now:] time did not allow earlier:] In addition, I wanted to ask if the better transmission diode (IR) 30 degrees or 60. As a phototransistor I wanted to use LTR4206E

This is exactly what I wanted to model: (I don't know the author I have been on disk for over a year, so I don't remember)

congratulations on the construction, I have a question: can you build a collecting pulsoximeter
satO2 from the ventricles of the heart, in addition to such a detector to work with an ultrasound head for heart examination, measuring depth 4-5cm from the skin, if the purpose of such measurements is unclear, please contact me by email: lancet(_at_)me.com or tel 603601401
pzdr