Studio shows electrode contact in the Devices window (Windows > Add > Devices). What you see depends on the device.
What each device shows
Section titled “What each device shows”| Device | kOhm values | Colours | How to start |
|---|---|---|---|
| eego 8ch, 32ch, 64ch | Yes, reported by the amplifier | During the test only | Test button |
| Discovery 20 | Yes, reported by the device | During the test only | Test button |
| Mitsar EEG 201 | Yes, reported by the connector. See Mitsar | During the test only | Test button |
| OpenBCI, OpenBCI + Daisy | Yes, but estimated from the signal | Always on | Nothing to start. There is no Test button |
| InteraXon Muse | No, the cells stay blank | Always on, from the headset | Nothing to start. There is no Test button |
| Neurosity Notion, Neurosity Crown, Versus, Test Device, BrainFlow boards | No | No | No check available |
The eego driver is in Windows and Linux builds. The Mitsar driver is Windows only. The Discovery 20 driver is only in the Windows x86 package. See Biosensors.
Muse has no thresholds and no pass or fail result. Its colours come from the headset: Good, Fair, Poor or Very Bad per electrode, and No Signal on all electrodes when the headset reports no forehead contact.
Devices not in community builds:
- Emotiv, NeuroSky: Not in public build. Available through a source build (community) or a custom build (commercial clients). The vendor SDK is not in the repository. The code gives them colours and no kOhm values, like Muse.
- actiCHamp: Not in public build. Available through a source build (community) or a custom build (commercial clients). The source has only a driver skeleton with no data path, so a build must complete it. It shows no contact values today.
- ABM: Not in public build. Available through a source build (community) or a custom build (commercial clients). Windows 32-bit; vendor headers not in the repository. The code gives it colours on the head plot, based on the EMG and artifact content of each channel. It has no kOhm grid.
- Brainquiry: Not in public build. Available through a source build (community) or a custom build (commercial clients). Windows 32-bit; vendor headers not in the repository. The code gives it no contact display.
Run the test
Section titled “Run the test”This applies to eego, Discovery 20 and Mitsar. OpenBCI shows the same display all the time, so use only steps 4 and 5.
- Connect the device and open the Devices window.
- Make sure no session is running. The Test button is disabled during a session.
- Click Test. The button changes to Stop, and the Impedance Test panel and the kOhm grid appear. For Mitsar, Studio restarts the connector in impedance mode. For Discovery 20, Studio resets the device.
- Under Threshold, pick a profile. Neurofeedback is selected by default, and your choice is not saved.
- Adjust the electrodes until they show a passing colour. Passed shows a success or failure icon.
- Click Stop before you click Begin Session. The colours return to blue and the grid closes.
Warning: Studio does not stop you from beginning a session during a test, and the Stop button stays disabled until the session ends. While a test runs, eego and Discovery 20 channels carry kOhm values instead of EEG, and Mitsar impedance messages add no EEG samples.
Colours and profiles
Section titled “Colours and profiles”The profile sets the limits in kOhm. Each limit is included in its band, so exactly 10 kOhm is Good under Neurofeedback. The Threshold tooltip writes these limits with “<”.
| Colour | Quality | Research | Neurofeedback (default) | Testing | Result |
|---|---|---|---|---|---|
| Green | Excellent | below 0.1 | below 0.1 | below 0.1 | Pass |
| Green | Good | up to 5 | up to 10 | up to 100 | Pass |
| Yellow | Fair | up to 10 | up to 20 | up to 200 | Pass |
| Orange | Poor | up to 20 | up to 40 | up to 300 | Fail |
| Red | Very Bad | up to 80 | up to 80 | up to 400 | Fail |
| Grey | No Signal | above 80, or no reading | above 80, or no reading | above 400, or no reading | Fail |
- Excellent and Good use the same green. Read the kOhm value to tell them apart.
- A value above the red limit is grey, not red. A very high reading looks the same as no reading.
- Blue means Studio has no contact quality for that electrode. It says nothing about the contact. You see it on the head plot of devices with no check, and of devices with a Test button when no test runs.
- Electrodes the loaded classifier doesn’t use look darker.
In 1.7.3: The limits and profiles are the same, but there is no Excellent level. A value below 0.1 kOhm is blank and counts as No Signal, so it is grey and fails. In 1.8.2 it is green and passes.
Pass or fail
Section titled “Pass or fail”The test fails if any checked electrode is Poor, Very Bad or No Signal. Excellent, Good and Fair pass.
- If the loaded classifier uses any electrodes, only those are checked.
- Otherwise, all electrodes are checked, including those beyond the first 8.
The result is for your information. It doesn’t block a session.
What the display covers
Section titled “What the display covers”- kOhm grid: Lists the first 8 electrodes only, with MIN, AVG and MAX below them. MIN, AVG and MAX use the listed electrodes the classifier uses, or all listed electrodes if it uses none. A device with more than 8 electrodes can fail the test while every listed row looks fine. eego amplifiers also count REF and GND as electrodes, so this applies to the eego 8ch too: REF and GND are checked but not listed in the grid. Check the head plot, but note that REF and GND share one position there, so one covers the other. Signal Quality under the Info button includes both.
- Head plot: Shows the colour of every electrode. OpenBCI has no head plot, so on OpenBCI + Daisy channels 9 to 16 have no display of their own.
- Info button: Under EEG Sensors, Signal Quality shows the worst quality across all electrodes as text. It shows “n/a” when contact quality isn’t available.
A kOhm cell is blank until the channel has delivered samples. Once a channel has had no sample for 2 seconds, its cell goes blank, it reads No Signal, and it drops out of MIN, AVG and MAX. Studio only runs this 2 second check while the loaded classifier reads from that device through a device node with Raw Output off, which is the default. Without such a classifier, a channel that has gone quiet keeps its last value.
In 1.7.3: There is no 2 second check. A channel that goes quiet keeps its last value and colour, and still counts in MIN, AVG and MAX. Those three values are blank below 0.1 kOhm.
OpenBCI values are estimates
Section titled “OpenBCI values are estimates”The OpenBCI driver computes its kOhm value from the EEG signal. It is not a lead-off measurement. Studio sends no lead-off or impedance command to the board.
For each channel, the formula takes the mean absolute deviation over the last second, multiplies it by the square root of 2, and divides by an assumed drive current of 6 nA. It then subtracts 2.2 kOhm for the board’s series resistor, with a floor of 0.
So the value follows the size of the signal, not only the quality of the contact:
- A mean deviation of 10 µV reads about 0.2 kOhm, and about 52 µV reads 10 kOhm.
- Blinks, movement and mains noise raise the value.
- A flat channel reads 0.0, which is green and passes.
Treat the value as a rough signal check. For a measured impedance, use a tool that runs a lead-off test, such as the vendor’s software. The estimate applies only to the OpenBCI driver in Studio. A Cyton connected through BrainFlow has no contact display.
Mitsar
Section titled “Mitsar”In impedance mode, Studio reads values from the Mitsar connector’s impedance messages, and those messages add no samples to the EEG channels. If the loaded classifier reads from the Mitsar with Raw Output off, the 2 second check then treats every channel as quiet, so the grid may go blank and the test may fail with No Signal. With no such classifier loaded, channels that delivered samples before the test keep showing values.
In 1.7.3: There is no 2 second check, so this does not apply.