help

[Ray.R]

Are you using an Optical sensor (typically for O2 content)?  If so and you have a differential Amp, then I do not understand why you need to amplify an electrode.  Do you also use an electrode to monitor ECG?   From what I read in your last post, you are attempting this without an electrode, so therefore the preamp would not be of any use.  However, I am not sure how you can detect cardiac rythm with optical sensors... unless you can create a flow way of some sort.  Then again, I've been away from this for many years...

So the "short answer" would be "no need for the preamp" if you do not use electrodes and you are happy with the signal from the optical sensor (ie: detectable waveform).

[akin]

thanks for that i really appreciate u clarifying it.Well to be honest wit u i ave decided on my speicfication and i dont need a pre amp.My specifications are

    1   phototransistor and infrared emitting diode act as the transducer .Electrodes cant be used cos of the current dat passes thru.rememba dis jus a finaly year project so we dont wanna rick nebody health.

    2   op-amp and bandpass filter: the bandpass filter will filter out all the nosie dats might interfere with the signal.This will compres of lowpass and high pass and the op amp will have a high gain,input impedance and high CMRR.

   3   DAQ for data acquisition interfacing 2 computer

   4   labVIEW software dis will display the heart  rate plus the pulse rate and maybe the blood pressure if dats possible to do.

What do u think about the specification ?Am i on the right track and frame of mind.

[AnalogKid2DigitalMan]

akin

If the LED/phototransistor approach will yield a usable signal, I suggest you start out testing that portion, then add the OP-AMP stage and test it, and then finally add/test the filtering portion. Try to do all the testing at these stages with an oscilloscope, if possible. When you are satisfied with the results from your circuit, then connect up to the DAQ card and start acquiring in LabVIEW. Such an approach will probably save time and confusion by not attempting to do the hardware/software design and debug at the same time.

Other approaches for noncontact heart rate monitoring-

-Accelerometer applied to the chest area or neck arteries

-Laser beam deflection off of a mirror attached to the subject

-Very low frequency microphone transducer

The first two of the 3 may require the subject to remain somewhat still- do not know if this is acceptable for your project.

[Ray.R]

Good suggestions AKTDM,

I don't think an Optical sensor can give any indication to blood pressure.  I'd be surprised if it did. 

[AnalogKid2DigitalMan]

JLV:

Hey, with enough light (or coffee), anything is possible

[Ray.R]

LOL!

🙂