Contact check#

The contact check measures how well each electrode is touching the scalp before you record. You reach it with the Impedance button on a connected, non-streaming headset card (see Connect a headset). The headset switches into impedance mode: it injects a small known current and reports electrode impedance in kΩ instead of EEG.

Warning

The contact check is a real headset mode change, not a display option. Entering and leaving it resets the Bluetooth link and stops any EEG stream — you will briefly see a “reconnecting” screen.

Layout#

The head map sits on top with the nose at the top of the screen, then the band legend, then the table. In landscape the head map moves to the left and the table to the right.

  • Each electrode is a disc at its 10-20 position showing its name and its reading in kΩ.

  • Discs pulse grey until they report. Electrodes whose labels are not standard 10-20 names are placed on a ring instead.

  • The pill at the top left shows n/N good once readings arrive (Measuring… before that).

  • The table is sorted worst first, with electrodes that have not reported at the top.

Note

The n/N good pill counts only the electrodes that have actually reported. Check the table as well — an electrode that has not reported yet is not counted in the pill.

Reading the bands#

Band

Range

Label

What to do

Green

< 200 kΩ

Good

Ready to record

Amber

< 400 kΩ

Check

Usable; improve it if you can

Red

≤ 600 kΩ

Poor

Re-seat before recording

Black

> 600 kΩ

No contact

Electrode is not reaching the scalp

Readings at or above 999 kΩ show as 999+.

Status line#

The status line reads State: … · Battery: … · lower kΩ = better contact. State is the Bluetooth link state; it reads Streaming during a contact check because the headset is streaming impedance values.

Getting good contact#

Press each electrode firmly onto the skin and part the hair underneath so it reaches the scalp. Make sure the reference/ground electrode is seated first — a bad reference degrades every channel.

Leaving the screen#

Control

Result

Stop (top bar) or Back

Returns to the device list and puts the headset back into normal mode

Stream (bottom)

Switches to EEG streaming and opens the viewer

Record (bottom)

Switches to EEG streaming, opens the viewer and starts recording

Both bottom buttons wait until the headset is settled before they become active.

See also#