Oximeter frames against SNUADC¶

The oximeter's 33.3 ms frame period is fixed per setup against the SNUADC sample clock, +7 to +92 ppm across 42 PC keys, and keeps its phase through the sawtooth slips.


Clock	Pulse oximeter frame clock
Measured against	SNUADC sample clock
Modes	all
Status	measured
Drift	+7 to +92 ppm by setup (medians over 42 PC keys); within 3 ppm of its setup's median in 89% of recordings

Parameters¶

Parameter	Value	Status	From
Oximeter frame clock against SNUADC	+7 to +92 ppm by setup (medians over 42 PC keys); within 3 ppm of its setup's median in 89% of recordings	measured	The PPG's 30 Hz frame clock

Evidence¶

Study	Date	Status	Summary
The PPG's 30 Hz frame clock	2026-10-10	current	ECG and PPG fiducials resolve to one 2 ms sample, but PPG fiducials taken on raw samples lock to a hidden 33.3 ms frame grid. Scanning for it finds the oximeter's frame clock to about 1 ppm, a fixed fingerprint of each recording setup.