Signal quality#

Signal quality scores every electrode while you stream, so you can see what is wrong with a channel and read the specific fix. Open it with the Quality chip in the viewer, the Quality button on the device card (see Connect a headset), or by tapping the N/M good chip.

Note

Opening signal quality does not interrupt the stream and does not change any mode — unlike the Contact check check.

Each electrode gets a quality index from 0 to 1 — lower is cleaner — recomputed about once a second from a four-second window of raw signal.

Note

Quality is always computed from the raw signal, so display filter settings cannot change it. Electrode contact is the one thing that does: a disconnected channel is scored unusable, drawn flat, and its PTP reads 0 µV.

Reading the bands#

Band

Range

Table label

Meaning

Green

< 0.55

Good

Clean — recordable

Amber

< 0.85

Check

Usable but noisy, or still settling

Red

≥ 0.85

Poor

Fix before recording

Purple

—

Railed

No usable signal — re-seat the electrode

  • Pill at the top: n/N good.

  • Head map: same 10-20 layout as the Contact check check, coloured by band. Tap any electrode for its details.

  • Table: CH and SIGNAL headers are sort buttons (worst-first by default). Tap a row or its chevron for details.

  • ⓘ in the top bar opens Reading signal quality — the bands and the common fixes.

  • The status line warns short gap-free window — quality may read optimistically if the score had to be computed from less than the full window (usually right after a dropout).

Per-channel details#

Tapping a channel opens a sheet with its score, a diagnosis, a specific fix, and the underlying numbers:

Row

Meaning

Contact

Connected / Not connected, as reported by the headset

DC offset

Electrode offset voltage in µV

Line noise (50/60 Hz)

Energy in the mains band

Broadband (0.5–40 Hz)

Energy across the EEG band

Amplitude (p-p)

Peak-to-peak amplitude of the displayed window

Diagnoses and their fixes:

Diagnosis

Fix shown

No contact

Re-seat the electrode: press it firmly to the skin and part the hair underneath so it reaches the scalp

No usable signal (railed)

The channel is railed or saturated: re-seat the electrode against the skin and check that its lead is not pulled or shorted

Mains interference

50/60 Hz pickup. Check the reference/ground electrode and move away from chargers and power cables

Movement or broadband noise

Stay still and make sure the electrode is snug — loose contact and motion show up here

Electrode offset or drift

Let it settle for a few seconds, or lift and re-seat the electrode firmly against the skin

Measuring…

Hold still while the signal settles

Good signal

No action needed

See also#