We are developing a new device to perform a new type of signal processing of finger photoplethysmography. We would like to use existing off-the-shelf clip SPO2 sensor.The interface characteristics, usually a 5/6 pin connector (Red/IR led power and ground; photosensor signal and ground, shield) but I did not succeed in obtaining the specs in terms of power requirements and of output signal range.
Nellcor is also Nonin clip compatible.
Power and output signal depends a lot on LED specs, Patient to patient differences and ambient light.
Many implementations have an optimization routine on LED current to maximize the output, which is in the order of 200uV (which is on top of the 0,6V of the diode voltage).
HTH,
Loek
Check out here from TI site: http://www.ti.com/lit/an/slaa274b/slaa274b.pdf
Hope it helps!!
Forgot to mention that I measured the output voltage with a (too cheap) voltmeter.
Actually the incident (infra)red light creates electron-hole pairs in the pn-layer, therefore modelling the PIN diiode as a current sources is a common way to go. Then one usually connects this current to an Operational Transconductance Amplifier.
For my own means it was enough to measure the voltage that the photocurrent induced over a resistor.