SNUADC values are truncated to the count below¶
The SNUADC firmware truncates each calibrated value instead of rounding it, so every value sits half a count low on average (about 0.5 mmHg for arterial pressure). Values clamp at counts 0 and 1023.
| Status | likely: consistent, with a known gap. |
| Devices | SNUADC |
| Variables | Arterial pressure (SNUADC), ECG lead II (SNUADC), Plethysmogram (SNUADC) |
What it means¶
A small constant bias, and clipping at the monitor's ±4 V output limits (arterial pressure near 400 mmHg).
Evidence¶
| Study | Date | Status | Summary |
|---|---|---|---|
| The SNUADC firmware | 2026-10-13 | current | The public SNUADC firmware explains the board's timing: it sends no time stamps, samples on its 16 MHz crystal, loses time rather than bunching samples after a stall, reads its channels one after another, and truncates its values. A predicted fault at the microsecond counter's wrap was not found in the data. |