Operating Instructions

Operating modes

Mentalab Explore+ has two main operating modes: offline and online. When in offline mode, the amplifier collects data and stores it in internal flash memory. Users can extract the recordings from the memory using a USB-C cable after recording.
In online mode, data is transmitted via Bluetooth in real-time to a host machine, enabling the user to collect, monitor, and visualize data. In this mode, you can also measure impedances, and configure the amplifier with explorepy and exploreAndroid. In online mode, the Explore+ amplifier sends signal data to the host machine. It also sends meta-data when the amplifier’s settings change.
We recommend charging the amplifier for at least one hour before first use. To charge the amplifier, connect the USB-C cable to a compliant source. A green LED indicates sufficient battery. After charging, unplug your amplifier from the power source.

Pre-experiment checklist

We strongly recommend completing this checklist before you start collecting EEG data. This will ensure you get the best out of your Explore+ system.

1. Install software

Install the software appropriate for your needs. An overview of our open-source APIs can be found on the software page of our website or in our GitHub Repo.
To verify impedances, you will need explorepy or explore-android. To download explorepy, please consult our explorepy Installation Guide, or download our Windows installer. To download explore-android, please consult the explore-android GitHub repository. Alternatively, use our user-friendly application: Explore Desktop.

2. Set-up equipment

Place the measurement electrodes on your subject in your preferred configuration. Each channel (1 – 8; 1 – 16; 1 – 32) is recorded against the reference electrode. For convenience, channel names are marked with tags.
Push the button to turn on your Explore+ system. At system start, the LED will illuminate blue. This indicates the amplifier is booting up. After boot up, the LED will present battery information (green: > 60%, yellow: 30 – 60%, red: < 30% charge remaining).
Upon normal start up, the amplifier begins to record to flash memory immediately. It starts advertising and waits for a Bluetooth connection to a host machine. During advertising mode, the LED blinks blue twice per second. If no connection is established within four minutes, the amplifier will automatically change to offline mode. In this state, the LED blinks green once every 3 seconds. Explore+ will keep recording data to internal memory.

Remember to remove all other Bluetooth devices from your Windows menu if you are using Windows OS. Disconnecting is not enough, they must be completely removed. Corded accessories, like mouse and keyboard, even if they have a Bluetooth adaptor, are fine.

If you press the amplifier’s button once during recording, a marker, with timestamp, will be sent to the host machine and written to internal memory. This can be used for labeling certain events, for example the beginning and end of recording periods.

To turn off the amplifier, keep the button pressed until the LED turns red. The amplifier will shut down with three red blinks.

3. Place the REF electrode

Position: For most EEG applications, we recommend placing the REF on the mastoid (TP9 or TP10). This will minimize artifacts from non-relevant brain activity, EMG, and ECG activity.
Application: Clean the mastoid with alcohol and abrasive gel. Either tuck the REF electrode under the EEG cap behind the ear (you can use tape here), or use the TP9 or TP10 positions in the EEG cap.
- Gel electrodes: Apply a generous amount of conductive gel onto the REF electrode.
- Dry electrodes: Apply some disinfectant onto the electrode. If you have trouble lowering overall impedances, you can apply a little conductive gel or paste to the REF electrode.

4. Check impedances

Before anything, if you are using the Explore Desktop application, ensure that you first view the signal using the signal pane before moving to the impedance measurement.

Unlike your raw ExG data, impedance measurements are fully online and so are prone to Bluetooth errors. Bluetooth uses the same frequency band as WiFi and ISM (Industrial Scientific and Medical). Additionally, old electronic devices can radiate disturbing frequencies.

If there is too much noise, your impedance measurements will be wrong. Aim to reduce noisy signals.

The lower the impedances, the higher the signal quality. Verify good impedances before recording. For detailed information on the impedance measurement, please watch our video guide, and see our explorepy documentation.

It is normal for dry electrodes to show high impedance values.

Impedance values are the sum of the impedances on the REF electrode and each individual channel. E.g. If your goal impedance is 15kΩ per channel, aim for about 30kΩ (REF + half channel).

If you are having trouble identifying which channel you are testing, move a single electrode. This will allow you to identify the signal.

3. If you need to improve your impedances, please have a read of our Improving Impedances page.

On the lower left corner of the Explore Desktop application, black text will indicate if the connection is stable during your impedance measurement. If not, consider the impedance measurement incorrect.

You are now ready to start recording EEG data. For information on how to visualize and record data using explorepy see our documentation and videos.