Timing Verification
The T1 Timing Harness is not a training feature. It is how you verify that the instrument is still measuring what it claims to measure.
When to run it
Section titled “When to run it”- On a new iPad, before any real session
- After an iPadOS update
- Whenever a threshold looks wrong
- If a session reports many timing-invalid trials
Before you start
Section titled “Before you start”Run on the physical iPad, unplugged from any computer, at normal screen brightness, with no other apps active. A device connected to a debugger does not perform like a device in the field.
T1 — Timing
Section titled “T1 — Timing”Verifies that the screen blacks out when commanded.
- Tap T1 Timing Harness from the home screen
- Select T1 · Timing
- Set trials to 200
- Tap Run
The screen shows the device model, the real refresh rate, and the clip duration while it runs.
Acceptance
Section titled “Acceptance”| Metric | Target |
|---|---|
| Median |deviation| | ≤ 8 ms |
| p95 |deviation| | ≤ 17 ms |
| Any deviation > 34 ms | 0 |
A green PASS banner means the instrument is sound. A red FAIL means thresholds measured on this device are not trustworthy — stop and investigate.
Reference measurement on the target iPad (iPad15,7, 60 Hz): median 3.4 ms, p95 5.3 ms, zero deviations over 34 ms.
T2 — Response
Section titled “T2 — Response”Verifies the touch-timing path.
- Select T2 · Response
- Set trials to 50
- Tap Run
- Tap any zone the instant the screen goes black. Which zone does not matter — this measures the response path, not anticipation
Acceptance
Section titled “Acceptance”| Check | Target |
|---|---|
| Negative RT | 0 — a negative value means a clock defect |
| RT over 1000 ms | 0 |
| Median RT | Plausibly 200–350 ms |
Three outcomes: PASS, Invariants OK but RT range implausible (amber — the clock is sound but the operator wasn’t tapping consistently), or INVARIANT VIOLATED (dark red — a real defect).
Reading the numbers
Section titled “Reading the numbers”| Row | Meaning |
|---|---|
| Median |deviation| | Typical blackout error. Red if > 8 ms |
| p95 |deviation| | Worst-case in normal operation. Red if > 17 ms |
| Max |deviation| | Single worst trial |
| Mean (signed, = bias) | Systematic offset. Correctable |
| SD | Scatter. Not correctable |
| Over 34 ms | Hard failures. Must be 0 |
| Invalid (>2 refreshes) | Trials that would be excluded from a real threshold |
Read bias and scatter separately. A consistent 5 ms late bias is a different problem from a 5 ms standard deviation, and only one of them can be tuned away.
Exporting
Section titled “Exporting”Tap Export report. This writes a CSV plus a Markdown report to the app’s Documents folder and opens the iOS share sheet.
- CSV — one row per trial with every measured value. Timeouts are left blank, not zero, so a spreadsheet cannot confuse them with an instant tap
- Markdown — metadata, an acceptance table with per-metric PASS/FAIL, a distribution table, a histogram of signed deviation, a per-offset breakdown, and display-link health