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SNUADC against the PC-stamped heart rate

The Solar8000 heart rate is stamped by the recorder on arrival, so the delay from the ECG to it, on the ECG's raw sample count, ramps at the SNUADC clock's rate: −65.3 ppm, against −66.7 ppm from the stamp model. Two independent routes agree.
Date 2026-10-17
Status current
Methods One event, two clocks
Clocks SNUADC sample clock, Recorder PC clock
Devices SNUADC, Solar8000 monitor
Variables ECG lead II (SNUADC), Solar8000 heart rate

Data

66 step-mode cases without gaps (722 thirty-minute blocks); 7 frequent-correction cases without gaps.

Method

The delay from the ECG to the Solar8000 HR was measured in 30-minute blocks with the ECG on its raw sample count and, separately, on the stamp-model line.

Results

  • On the sample count the delay ramps at −65.3 ± 3.9 ppm; the stamp model gives −66.7 ppm median for the same cases.
  • On the corrected line the ramp is −13.0 ± 4.0 ppm: small, not quite zero. A residual to watch.
  • Frequent-correction cases are inconclusive here (7 cases, 52 ± 40 ppm).
  • Per-case precision is poor: block delays scatter by about 0.7 s, so this works pooled, not per case.

Discussion

A second, independent measure of the SNUADC–PC rate, through a device with no clock of its own.

Open questions

  • A residual of −13 ppm (unexplained phenomenon). On the corrected SNUADC line the ECG-to-HR delay still ramps by −13.0 ± 4.0 ppm. It may be the Solar8000's own processing, an error in the stamp model's rate, or the PC; a larger run (all step-mode cases without gaps) would narrow it. The whole-release run (The SNUADC clock through the Solar8000 numerics, whole release) cannot settle it: per recording it is too noisy, and in recordings under about 4 h its rate is biased toward zero.
  • Frequent-correction mode on more cases (next step). Frequent-correction mode is inconclusive on 7 cases (52 ± 40 ppm).

Code