CardioQ FLOW uses three scales (a segmented code)¶

CardioQ FLOW values step by 1 from 0 to 255, by 2 from 256 to 510 and by 4 from 512 to 1016: 509 values, a 9-bit code whose step doubles in each upper segment, as in µ-law and A-law companding or a small floating-point format (an exponent and a 7-bit mantissa). Below 256, even values outnumber odd ones by 40 to 230 times.


Status	likely: consistent, with a known gap.
Devices	CardioQ

What it means¶

The resolution depends on the value, so each sample's quantisation uncertainty does too: step 1 below 256, 2 from 256, 4 from 512 (1 SD = step/√12: 0.29, 0.58 and 1.15 units). Below 256 the even-value comb makes the effective step mostly 2 (1 SD 0.58). A per-sample uncertainty model must take the step from the value, not one step per track.

What is done about it¶

Not modelled yet. The FLOW unit and the device's encoding are not documented in the release; the Deltex interface specification would settle both.

Evidence¶

Study	Date	Status	Summary
Value resolution of every signal	2026-10-19	draft	How finely every waveform and numeric track in the release records its values. The SNUADC waveforms are 10-bit codes, though VitalRecorder's documentation describes the SNUADC as 12-bit; Primus waveforms use about 10 bits of 12; BIS EEG is a 16-bit grid of 0.05 µV. Numerics are 32-bit floats on decimal grids of 1, 0.1, 0.01 or 0.001, one per track; settings sit on coarser grids of 10 or 100.

Figures¶

Left, a dense comb of lines from 0 to 1016 whose spacing widens at 256 and 512. Right, tall blue bars on even values and short orange bars on odd ones. — Left: every stored CardioQ FLOW value over the 29 recordings, one line per value, log count. The spacing doubles at 256 and again at 512. Right: values 100–140: even values (blue) hold about a hundred times more samples than odd ones (orange).