Three Instrument Floors: null calibration of a composite EEG/HRV index on consumer hardware

A composite real-time index built from consumer EEG and heart-rate variability returns a number on any input, including input containing nothing. This paper measures what each factor of such an index returns on structureless input pushed through the identical processing chain, so the floor carries every artifact the real pipeline carries. Reports the measured floors, a corrected signal-to-noise estimate, the effect of channel clipping and dropout, within-recording window independence, and the limits of what a single recording can establish. All numbers reproduce from one raw capture and the shipped scripts.