system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the machine measure oxygenation through the skin of your finger?

I was at the doctors with my kid and the nurse put a clip over his finger wich was hooked to a monitor. How can it measure pulse and oxygenation?

PS: I am a first time poster and english is not my native tongue. Be gentle:)
gpt
The process is called "Pulse oximetry".  To simplify the way it works, the device which is placed somewhere on the body where the skin is thin, in your case the finger, and it emits specific light wave lengths, and its sensors detects what waves are being absorbed through the blood, giving them a fairly accurate approximation of the oxygenation of your blood.