> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usefusion.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Signal Quality

> Monitor electrode contact quality in real-time during EEG recording

# Signal Quality

Good EEG data starts with good electrode contact. The recordings page shows real-time signal quality metrics during active recording so you can adjust headset fit before capturing important data.

## How It Works

Signal quality is calculated from the **standard deviation** of voltage values over a 1-second sliding window (256 samples at 256 Hz). Lower deviation means cleaner, more stable signal.

| Standard Deviation (µV) | Rating     | Bar Color | Meaning                           |
| ----------------------- | ---------- | --------- | --------------------------------- |
| 1.5 – 10                | Great      | 🟩 Green  | Clean neural signal, good contact |
| 10 – 15                 | Good       | 🟨 Yellow | Acceptable, minor noise           |
| > 15                    | Poor       | 🟥 Red    | High noise, adjust electrode      |
| \< 1.5                  | No contact | ⬜ Gray    | Electrode not touching scalp      |

## Quality Panel

During recording, two views appear:

### Bar Chart

A per-channel bar chart updating every second. Each bar is colored by the quality rating above. Aim for mostly green bars before starting your real recording.

### Brain Montage (2D)

A top-down head diagram (nose at top) showing electrode positions from the 10-20 system. Each electrode dot is colored by its current quality rating, giving you a spatial sense of where contact is poor.

## Tips for Good Signal

<CardGroup cols={2}>
  <Card title="Neurosity Crown" icon="brain">
    * Dampen the rubber sensors with saline or water
    * Press the band firmly against the back of your head
    * Check that forehead sensors (F5, F6) have contact — push hair aside if needed
    * Sit still for 5 seconds and watch the quality bars settle
  </Card>

  <Card title="Muse Headband" icon="head-side-brain">
    * Ensure the forehead sensors (AF7, AF8) sit flat on skin, not on hair
    * The ear sensors (TP9, TP10) should press firmly behind each ear
    * Tighten the band if temporal channels show poor quality
    * Relax your jaw — jaw clenching adds muscle artifacts
  </Card>
</CardGroup>

## When to Start Recording

* **All green**: Ideal — start immediately
* **Mostly green, one yellow**: Acceptable for most analyses. ZUNA can clean mild artifacts
* **Red or gray channels**: Adjust the headset. Red means high noise; gray means no contact at all

<Warning>
  ZUNA can remove many artifacts, but it works best when the raw signal has decent contact quality. Starting with poor signal quality means losing neural information that can't be recovered.
</Warning>