Clocks¶

Anything that keeps time: a crystal, a computer clock, a frame clock, a pacemaker.


BIS clock	The BIS monitor's own clock.
CardioQ clock	The CardioQ's own clock; the recorder re-anchors its stamps about every 5 minutes.
Hospital records clock	The clocks of the anaesthesia record and the laboratory system, and the rounding of what was entered.
Monitor analogue output clock	A line at 240 Hz in the arterial pressure and plethysmogram (weakly in the ECG) runs −25 to −29 ppm against the SNUADC sample clock: most likely the patient monitor's output stage.
Pacemaker clock	The crystal of an implanted pacemaker. At a fixed pacing rate it beats at one constant interval that no device in the recording chain can touch, which makes it an independent reference.
Primus clock	The Primus anaesthesia machine's own clock.
Pulse oximeter frame clock	The oximeter module plays the plethysmogram out in 33.3 ms (30 Hz) frames on its own clock, fixed per recording setup at +7 to +92 ppm against the SNUADC sample clock (medians over 42 PC keys).
Recorder PC clock	The Windows clock of the PC running Vital Recorder. It stamps every record, and every other clock is linked to it, directly or through others.
SNUADC sample clock	The sample clock of the SNUADC acquisition board, which digitises ECG, arterial pressure, plethysmogram and CVP at 500 Hz. The working reference for every waveform alignment.
Solar8000 clock	The Solar8000 monitor's internal timing of its numeric windows.
UTC	Coordinated Universal Time, the reference every chain of clocks in the atlas starts from.