Primus clock¶
The Primus anaesthesia machine's own clock.
Stub
Imported from the time-source table; the full page is still to be written.
| Type | oscillator |
| Nominal | 62.5 Hz waveform clock |
| Kept by | Primus anaesthesia machine |
Description¶
The Primus anaesthesia machine's own clock. Its stamps are re-anchored at recording gaps and by small corrections about every two hours. Measured by breath matching, it drifts a median +104 ppm against the recorder PC, which its small corrections do not keep up with.
Route to UTC¶
The route the atlas trusts most (2 links; its weakest link is measured apart from the link to UTC that every clock shares):
link measured Primus against the recorder PC: drift 104 ppm (p10–p90 28 to 184; 178 recordings; whole-recording lines give +87 ppm median in 1,060 (p10–p90 −49 to +229)); corrected every about 7,230 s (2.0 h; p90 twice that)
Where every route ends.
Plan. Measured to the PC by breath matching through the SNUADC stamp model: +104 ppm within the stretches between AWP pauses (p10–p90 +28 to +184, 178 recordings), with steps at the pauses that do not reset the drift: tens of ms where CO₂ carries on, up to seconds where CO₂ stops too (The Primus stamp step at each airway-pressure pause). The small correction steps imply only 1–11 ppm and are not the clock rate. Open: what re-anchors the stamps where CO₂ stops too; the airway-to-CVP physiological delay inside the measured lag.
Links to other clocks¶
| Link | Clock | Against | Modes | Rate | Corrected every | Status |
|---|---|---|---|---|---|---|
| Primus against the recorder PC | Primus clock | Recorder PC clock | all | 104 ppm (p10–p90 28 to 184; 178 recordings; whole-recording lines give +87 ppm median in 1,060 (p10–p90 −49 to +229)) | about 7,230 s (2.0 h; p90 twice that) | measured |
Variables spaced by this clock¶
Airway pressure (Primus), Capnogram (Primus)
Observations¶
| Observation | Status | Summary |
|---|---|---|
| The Primus AWP stops for about 21 s every 7,230 s | established | In 5,502 recordings the Primus airway-pressure waveform has gaps of 19–23.5 s (whole messages of 0.48 s, mostly 21.12 s) that recur every 7,230 s, the Primus's correction interval; a clock correction follows about 21.6 s after. The CO₂ waveform carries on through 90% of them. The 21 s of AWP are lost, not merely re-stamped. |
| A heartbeat-locked trace in the CO₂ waveform that ignores the Primus clock | open | Averaged on the ECG's R peaks, the Primus CO₂ waveform shows a heartbeat-locked signal in 60% of 10-minute windows (30-recording pilot), tight to about 20 ms. Unlike the breath, its lag does not drift with the Primus clock: it stays fixed on the SNUADC timeline. |
Studies¶
| Study | Date | Status | Summary |
|---|---|---|---|
| The heartbeat in the Primus airway signals | 2026-10-19 | current | A pilot in 30 recordings for a heartbeat-locked route from the Primus to the SNUADC. Airway pressure shows the heartbeat in 9% of windows only. CO₂ shows a heartbeat-locked trace in 60% of windows, tight to 20 ms, but its lag does not follow the Primus drift, so it cannot time the Primus. Closed as a clock route. |
| Gaps and unbroken segments in every waveform | 2026-10-19 | draft | Every gap and every unbroken segment in the 6,388 recordings, per waveform. The curves are not smooth: a cliff at about 18 s in every device marks the recorder's pauses, SNUADC segments stop at 5 hours, Primus segments at about 2.0 hours and BIS segments at about 2.3 hours (each device's correction cycle), and BIS's short gaps grow with the time since the last one (clock resynchronisations, not lost data). |
| When each device's clock is corrected, in every recording | 2026-10-19 | draft | From the steps between records in all 6,388 recordings: the BIS is corrected every 8,192 s and the Primus every 7,230 s, on their own timers (the first correction comes at any time after the device starts); the SNUADC is reset when 0.49 s of drift has built up. With the full rerun of the correction fit, it gives each device's drift against the recorder PC in 4,728 BIS and 2,728 SNUADC recordings, and shows that the Primus's 20–23 s AWP pauses belong to its correction cycle. Every rate here is relative to the recorder PC, whose own clock drifts and is corrected. |
| The Primus stamp step at each airway-pressure pause | 2026-10-19 | current | Measured directly at 2,491 pauses in 1,021 recordings: where CO₂ carries on through the AWP pause (74%), the Primus stamps barely step (median −1 ms, p10–p90 −164 to +187 ms, close to the no-pause controls); where CO₂ stops too (26%), they step by up to seconds. No step undoes the drift built up since the last pause. |
| Message sizes and the steps between records | 2026-10-19 | draft | Every record in every waveform: SNUADC writes messages of 100 samples (0.2 s), Primus 30 (0.48 s), BIS 16 (0.125 s), CardioQ no fixed size. Backward steps outnumber gaps by about a hundred to one and come from a few recordings with duplicated or interleaved records. Primus gaps are whole lost messages; most SNUADC and BIS gaps are not. |
| What each break in the stamps is | 2026-10-19 | draft | Every step between waveform records in the release, sorted by mechanism: written twice, a SNUADC clock reset, interleaved streams, a pause shared by every device, whole messages, less than a message, or a fraction of a message beyond whole ones. A continuity test with controls shows which classes lose data: shared pauses and most longer SNUADC gaps do; steps under one message, and SNUADC's lone one-message steps, mostly do not. |
| How often each device is corrected | 2026-10-17 | current | The devices re-synchronise in different ways: SNUADC when its drift reaches about half a second, BIS on a fixed 8,192 s timer, and the Primus by small steps about every two hours that do not keep up with its drift (+104 ppm, measured later by breath matching). |
| Closing loops in the timing graph | 2026-10-13 | current | Where two independent routes reach the same clock, the offsets around the loop must sum to zero. Three measured loops close within their noise; the BIS loop closes up to a constant latency; the proposed EMR loop is not a loop at all. |
| The Primus ventilator against SNUADC, by breaths | 2026-10-12 | open | Each breath shows in the Primus airway pressure and, through the chest, in SNUADC's central venous pressure. Tracking that lag puts the Primus on the SNUADC timeline to about 55 ms over the whole release, with a line per stretch between its AWP pauses (49 ms in the pilot). At scale it measures the Primus drifting a median +104 ppm against the recorder PC between its AWP pauses, with steps at the pauses that do not reset it. |
| 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. |
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