BIS against SNUADC¶

Measured directly from bursts seen in both the ECG and the EEG, independent of the recorder: −72 ppm (median of 191 benchmark cases), and a constant offset of about −0.8 s left after both stamp models. Per case the slope matches the difference of the two drifts against the PC (Shared bursts between the ECG and the EEG); the release medians of those drifts (+25 and −63 ppm) differ by 88 ppm, being medians over different sets of recordings.


Clock	BIS clock
Measured against	SNUADC sample clock
Modes	all
Status	measured
Drift	−72 ppm (IQR −82 to −54)

Correction¶

Both devices' own corrections: SNUADC on its drift threshold, BIS on its 8,192 s timer.

Parameters¶

Parameter	Value	Status	From
BIS drift against SNUADC	−72 ppm (IQR −82 to −54)	measured	Shared bursts between the ECG and the EEG
EEG–ECG constant after the stamp model	−804 ms in step mode (1,526 recordings); −660 ms in frequent-correction mode (78)	measured	The stamp sawtooth model for SNUADC and BIS
EEG–ECG timing error after the stamp model	42 ms median, p90 150 ms (17 ms and 79 ms with the recording's own bursts)	measured	The stamp sawtooth model for SNUADC and BIS

Evidence¶

Study	Date	Status	Summary
Shared bursts between the ECG and the EEG	2026-10-12	current	Electrocautery and muscle bursts appear in both the SNUADC ECG and the BIS EEG. Cross-correlating their envelopes gives the offset between the two devices' stamps every 10 minutes: about −0.8 s, in a sawtooth that follows both clocks' corrections.
The stamp sawtooth model for SNUADC and BIS	2026-10-12	current	Fitting each track's record stamps against its sample count as a drift with corrections (a sawtooth) puts SNUADC and BIS on one timeline without any artefact. Checked against shared bursts, the EEG–ECG timing error falls from about 790 ms on the recorded stamps to 33 ms with one constant per SNUADC mode in the pilot, and 42 ms over the whole release.