Brian noticed BE12599's 2026-08-09 event reports no ZC frequency because the
trace never crosses zero. That is the best detector in this investigation.
A geophone has no DC response, so its output must integrate to ~zero over a
record. |mean|/peak is therefore ~0 for real motion and ~1 for anything
electrical. Across 12,068 channel-events with peak >= 0.05 in/s the statistic
is bimodal with a 1.09% dead zone, and at mp >= 0.8 it returns exactly the five
confirmed units -- from physics rather than a tuned threshold. Two detectors on
different principles agreeing is the strongest corroboration the list has had.
It also settles BE11007 as NOT an offset: mp 0.75-0.89 but frac_neg 0.99 at
peaks of 7.4-9.4 in/s, i.e. a one-sided near-full-scale blast.
Journal 8e diagnoses BE12599 specifically. Its August waveforms are unipolar
impulses with an RC tail (26 ms -> 118 ms -> never recovers over 14 days), and
the fault MOVES between Long and Tran while the sensor self-check passes on
every event. A failing element cannot hop channels; a connector can -- which
also explains why the swing test never fails and why an autozero rarely helps.
Corrects 8c's claim that the spread gate is blind to onsets: of 87 BE18438|Vert
events it rejected one, the transitional record. Narrower than stated.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
Records the mechanism investigation in journal 8c. The headline: still unknown,
but the shape is now constrained and a long list of dead ends is closed.
Onset is a ramp of minutes-to-hours, not a step — BE18438 Vert resolved to
one-minute cadence via the histogram corpus, 50% of the excursion in 7 minutes,
>=25 intermediates, validated 75/75 against Blastware's own ASCII. That kills
both poles of the original dichotomy: not a latched digital step, not slow
component wear. What survives is a reversible two-time-constant settling
process, which is a shape constraint and not a mechanism.
Thermal, ground-motion shock, handling/redeployment, accumulated duty, age,
firmware and a mechanical element fault are each refuted or explicitly bounded,
with the power behind every negative stated.
Retracts two claims this journal carried: polarity consistency was a tautology
of offset_scan3's spread gate, and the fleet is 8-9 units rather than 5 once
that gate is dropped. Also notes the gate is blind to onsets by construction --
it rejects a moving floor, and it rejected the one record where the ramp shows.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
BA9229, BA10060, BA10895 and BA15957 were reported throughout as BE — the
scanners synthesised the family prefix, which the BW filename does not carry.
Corrected across the journal with a note recording why, so the mistake is
legible rather than silently patched.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
offset_scan3.py covers only waveforms (6,577 unique binaries). The archive
also holds 63,535 unique histograms, which the pre-trigger method cannot
touch: a histogram carries no samples, only a per-interval per-channel peak.
scratch/offset_hist_scan.py scans them — 63,505/63,535 decoded (99.95%),
43 units, 77.9M intervals. It emits every candidate floor statistic per
(file, channel) rather than deciding anything, so thresholds get calibrated
against the waveform ground truth instead of guessed.
Journal §8b records the outcome. What survives is a site-quiet-gated
cross-channel differential that independently confirms BE18438|Vert and
BE9558|Tran+Long with a clean 2.5x separation gap and 0.037% day-level false
alarm, threshold-insensitive across a 2.3x span — the first operating point
in this investigation to pass that test cleanly.
What it does not do, recorded just as plainly: it finds 2 of the 5 confirmed
units, not 5. DC leakage into the interval peak is bimodal (0.9 on BE18438,
0.02 on BE12599), so a negative histogram result is not evidence of health.
Per-channel attribution is not established (channel-scramble p = 0.769) and
timing resolves to ~a month, not a day.
Two dead ends buried for good: the absolute floor is retired (66% of its
discrimination is a day/site confound), and zero-fraction is structurally
impossible — the device clamps every interval peak at >= 1 A/D count.
Two findings independent of the histograms:
- offset_scan3's spread<=0.02 gate discards 18.8% of rows with |pre|>=0.025,
concentrated on 41 unit-channels currently labelled clean; 4 would be
sustained positives without it. The fleet label is three-state, not two.
- The waveform corpus observes ~7% of the days a unit was deployed.
BE10895 is reclassified from transient to a genuine Vert fault of a different
subtype: 49.4% single-axis-dominant events, the highest in the fleet, all on
Vert. The other six marginal units are clean.
Not done: the 11 thin-coverage units were not screened, and no completeness
audit was run.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
Brian's method, and better than v2's whole-record median: the pre-trigger
window is definitionally quiet (the buffer captured before the trigger fired),
whereas a median is merely robust to the event. Requiring the floor to hold
across pre-trigger / middle / end rejects transients that a median cannot.
per channel: pre/mid/end medians, spread = max - min
offset when |pre| >= floor AND spread <= 0.02 in/s
real fault >= 3 consecutive flagged events on that channel
The empirical noise floor justifies the threshold and validates the decoder:
across 19,244 non-flagged channel-events the pre-trigger floor is 62.7% exactly
0.000, 94.5% within +/-1 quantisation unit, median +0.0000, mean -0.0008. There
is no systematic zero-point bias — an independent confirmation of the
32000-count geo scale.
The result is threshold-insensitive across a 2x range (0.020 to 0.040 in/s),
which is what separates a real signal from a tuned one:
FINAL: 5 of 45 units (11%) — BE9558, BE11529, BE12599, BE13117, BE18438
BE11007 and BE10895 drop out; the spread test identifies them as transients
rather than pedestals. v1's 11% headline was right by luck — it included
BE11007 and named the wrong channel on most units.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
Brian challenged the v1 finding that offsets "come and go", against field
experience that a unit which develops one stays broken until the geophone is
replaced. He was right; v1 had two flaws, both of which manufactured false
recoveries:
1. It scored only the axis with the largest peak, so a real event on one axis
hid a persistent pedestal on another. BE12599 on 2026-08-21 read "clean"
because Long had a 1.065 in/s event, while Tran sat at +0.4732 in/s and was
never examined.
2. It used the mean, which a real transient perturbs. The median is the resting
baseline and a blast does not move it. Same event, Long channel:
mean +0.0783 vs median -0.0050.
offset_scan2.py flags a CHANNEL when |median| >= 0.025 in/s (5 A/D counts,
Instantel's own criterion) and treats >=3 consecutive flagged events as the
real signal. No m/p ratio guard is needed — that existed only to compensate for
the mean.
Corrected results:
units with any flagged event 6 -> 19 of 45
units with a sustained pedestal 8 of 45 (18%)
runs >=3 consecutive 29; 1-2 event runs (noise) 69
Also corrected: the affected channel is most often Vert, not Tran (v1 named
whichever axis had the largest peak, so it was frequently wrong). BE10895 and
BE18003 were invisible to v1. BE12599's fault began 2026-08-14, not 08-17.
The decode itself was never in question and is confirmed against Blastware's
own ASCII export: on K558LJN3.BK0W, BW shows Tran parked at +0.265..+0.375 in/s
for the entire record while Vert and Long sit at ~0.005 — Instantel's "parallel
lines above or below the zero line".
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
Adds docs/offset_investigation.md — a dated journal of the "offset" hardware
fault, in the style of the codec status docs: findings with provenance, dead
ends kept with the reason they died, and per-unit case files.
Contents:
- base rate 5-6 of 45 units (11-13%) over the DL2 archive, 2018-2026,
confirming rather than overturning the earlier 2-of-21 estimate
- the detector, with the rationale for each term and its known blind spot
(event traces carry real motion, so only trace-dominating offsets show)
- the bimodality result: relaxing the amplitude floor 11x adds no new units
- Instantel's own procedure and thresholds from their FAQs 13-0-21 / 12-0-10:
A/D-mode ">5 counts", the autozero key sequence, and the 2027-2069 X1/X8
acceptance window that explains the ~10% field success rate of a re-zero
- four ruled-out hypotheses, each with the evidence that killed it:
condensation, clipping, the sensor check as a predictor (102 offset events,
zero failures — a grossly offset unit passes its own self-check), and the
calibration-timing correlation (confounded, one unit per time bucket)
- open questions, chiefly whether SUB 0x0E carries the autozero numbers
Cross-referenced from CLAUDE.md and Appendix E of the protocol reference
(whose CRLF line endings are preserved).
Separately: CLAUDE.md had 793 NUL bytes appended after its last line. They
predate this work (present at least as far back as e42956a / v0.21.0) and made
grep treat the file as binary, silently skipping it. Stripped.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
serversdownandClaude Opus 5