All SNUADC channels share one clock¶
Every SNUADC waveform track of a case (ECG leads, ART, PLETH, CVP) has the same first stamp, the same record timing and the same corrections. They are stamped together.
| Status | established: shown on many cases, with a control. |
| Clocks | SNUADC sample clock |
| Devices | SNUADC |
| Variables | ECG lead II (SNUADC), Arterial pressure (SNUADC), Plethysmogram (SNUADC) |
What it means¶
Clock drift cancels between SNUADC channels: ECG, arterial pressure and plethysmogram line up to the sample, apart from the analogue paths behind them. A beat-alignment check between two SNUADC leads tests sample packing, not drift.
Evidence¶
| Study | Date | Status | Summary |
|---|---|---|---|
| Records out of order at SNUADC resets, and where the lost time goes | 2026-10-17 | current | At every SNUADC reset the five records after it are written out of order: two continue the old timing and three start the new. Put back in order, the waveform runs on with no samples missing; the 18–20 ms lost at each reset goes missing inside the last old-timing record, and an extra zero sample follows. |
| Time zeros and loaded subsets | 2026-10-16 | current | A VitalDB time "from the start" depends on which tracks were loaded: loading a subset moves the zero to that subset's first record, seconds or hours later. The arrhythmia database's annotations count from the full file's zero. |
| Clock corrections in every file | 2026-10-11 | current | A scan of all 6,388 files for the jumps where the recorder re-synchronises a device's stamps. Each device type has its own correction signature; only SNUADC and BIS correct clearly enough to measure their drift. |