Troubleshooting / Problem Solving
- 1 Noisy EEG recording
- 2 Stimulation
- 3 Troubleshooting connectivity issues with Bluetooth
Noisy EEG recording
When an EEG is started to be recorded using NIC software, the system needs a while to electrochemistry stabilize. After this time which normally takes less than a minute, if the EEG looks noisy, please read the following troubleshooting tricks and recommendations:
Some EEG channels are affected but not all of them
If not all the channels are at fault, unless you are using a DryTrode, add more gel and try to establish a good contact between the electrode and the scalp, removing some hair if you can. If this still does not work, try replacing the electrode/s. If the problem persists, please try to swap cables across two electrodes (one behaving well and one bad) to see if the faulty/noisy signal changes or remains at the same lead.
All the EEG channels are affected
If all EEG channels are noisy, please make sure the DRL/CMS electrodes are correctly setup and connected. Here some recommendations:
First, clean up the mastoid area where you are going to attach the CMS/DRL electrodes. You can use a paper napkin with some water or alcohol. Removing the grease and drying the skin will help you to get a good signal. Place the StickTrode adhesive electrodes close to each other with the DRL on the bottom, as the figure shows. Ensure the two electrodes are not touching each other. The CMS electrode should be on top of the mastoid bone to avoid contamination from blood vessels (ECG like signals). For the reference electrodes, the Earclip electrode can also be used connecting CMS and DRL cables at both clips, adding some gel at the sensors and clipping it to the earlobe.
Additionally, ensure you have a reasonable battery charge (>20%).
If you have a NE testboard, you can check that the necbox is functioning properly by connecting it to the testboard and observing signal quality in all channels. If a channel is misbehaving, contact our Technical Support team (firstname.lastname@example.org).
Please find in this section some recommendations when stimulating with a Starstim device and some troubleshooting tricks.
NIC is reporting high values of impedance
The Starstim is a stimulator device and, in order to deliver the programmed current, it calculates the impedance of each stimulation channel and they are displayed in NIC. The impedance bar appears below the icons of the stimulation channels and its color depends on the obtained value:
green: [0 - 10] kOhm
orange: [10 - 15] kOhm
red: [10 - 15] kOhm
For safety reasons, if the impedance is too high, the stimulation session will self-abort. So, if our system have high impedances, we won’t be able to run the protocol.
We always recommend running the impedance check before launching a stimulation protocol. If the impedance is too high (red tab), it might be related to the setup, the cables or the device. Below are some setup suggestions to follow in case of high impedances:
- Check that the DRL/CMS electrodes are correctly placed.
- Move the hair to ensure the contact between the electrode and the scalp.
- Make sure the hair is clean and free of sprays, oils, cream and lotions. Shampoo your hair and rinse with clear water the evening before or the morning of the test. Avoid hair conditioner or oil.
- Add more gel/saline solution to the electrodes.
- Ensure that you have a reasonable battery charge (>20%).
Note that impedance depends on skin type and can vary quite a bit across individuals.
Normally the measured impedances of the impedance check might be higher before stimulation, but when the experiment starts after some time they might fall down. This is normal because the stimulation can itself lower impedance.
In case you tried these recommendations and you couldn’t get lower impedances, please read the following section.
The NE Testboard
A good tool for debugging is our testboard. This board connects to your necbox and allows to test different system functionalities as well as discard problem areas.
A Neuroelectrics’ device connected to a testboard will respond as a system properly placed in a subject, with a very similar electrical environment, that is why we refer to it as an “artificial head”. This tool lets us know if the root cause of the high impedances issue is the device, the cables or the setup.
The testboard connected to a 8-channel Starstim
Using the flat cable connection as the picture shows, the eight channels of the system plus the CMS and DRL are connected to the testboard. As a result, all the channels are connected to this “ideal head of a subject” and, using this setup, the protocol shouldn’t be aborted due to high impedances. If the protocol is aborted, we can assume this issue comes from the device itself. In this case, please contact us. If the stimulation protocol can be run without problem, we know the issue doesn't come from the device and it may come from the cables or the setup.
In order to test the electrode cables, please see the following picture. Using the electrode cable connection, the CMS, the DRL and two channels are connected to the testboard. In this case, the channels 1 and 4 would be tested. So, we would create a bipolar stimulation protocol with channels 1 and 4 and see if it is aborting due to high impedances. If not, we would go checking all the cables (two at a time) trying to find if there is any faulty cable that is producing high impedances. In case there is a channel that is always reporting high impedances, this means the electrode cable is faulty.
The testboard connected to a 20-channel or a 32-channel Starstim
Unlike the 8-channel Starstim, the 20-channel and 32-channel Starstim has a specific slot for the CMS and DRL. For this reason, both channels are always connected to the clips of the testboard as the pictures shows. Despite this difference, the tests would be the same: connection with the flat cables to test the device (left) and connection with the electrode cables to the clips to test the electrode cables (right). For second test, remember to only enable in NIC those channels that would be connected to the testboard clips.
Measure the output current
This test intends to measure the actual currents delivered during stimulation. To perform this test you will need the following:
- Electrode cable
- Starstim (NECBox)
- USB connector
The idea is to measure the voltage level on certain resistors on the test board during the stimulation and to calculate the current being delivered.
1. Connect channels 1,6, CMS and DRL to the connector clips on the testboard as specified below:
- Ch1 - P1
- Ch6 - P2
- CMS - P3
- DRL - P4
Note: it is important to connect the electrodes in the correct order.
2. Connect the electrode lead cable to the NECBox. Note that the testboard is not the one that is directly connected.
3. Turn the device on and connect it to NIC.
4. Create a new protocol with two stimulation electrodes and launch it. Note that the stimulation channels defined in the software have to match those connected to the testboard (in this case channel 1 and channel 6).
5. Press the Play button and wait for the ramp-up to finish.
6. Turn the multimiter on and set it to the voltage measurement mode.
7. Measure the voltage drop across 4 components: RC1, RC2, RC9 and RC10. To do so, place the black lead of the multimeter on the outer terminal of the resistor and place the red lead on the terminal towards the center of the testboard, as shown in the picture below. Take a note of the voltage level displayed on the multimeter while paying attention to the sign.
8. Calculate the output current from the Ohm's Law (RC=4kOhm).
Troubleshooting connectivity issues with Bluetooth
The Enobio/StarStim NECBOX connects to the computer using the windows bluetooth stack. It is important to check if the computer has the Windows stack installed and working. This is not obvious when:
The computer is a Toshiba Laptop (it might use the Toshiba Stack) The computer has Windows XP (The stack depends on the dongle used)
If the computer has integrated bluetooth hardware, the system shall be used with their integrated bluetooth. Do not use the provided dongle in a computer that has integrated bluetooth (such as a Mac).
Some known problems and solutions
In Windows, after a certain time, the device doesn't connect anymore : remove the bluetooth device from the BT device manager and remove the associated COM ports from the device manager. Let NIC install them again.
When connecting to a new device, some computers show a message "a Bluetooth device is trying to connect". The user should click on this message and validate the connection. This message might be hidden, so the user should check on the bluetooth icon from Windows.
In Mac OS you may need to allow the system to run NIC. If needed (the system will ask you or tell you that app is not allowed), go to System Preferences as an administrator / Security & Privacy, and check the box Allowing apps downloaded from anywhere.
With some newer Mac laptops, bluetooth connectivity is affected by Wifi (seem like Apple is now using a single antenna for both bluetooth and wifi), so Wifi must be turned off while you use NIC. You can still use regular ethernet via cable, however (you may need to get a Thunderbolt to Ethernet adaptor).
With Maverick (the latest OS X release as of Nov 2013) and NIC v1.2.10 or before, you will need to disable the App Nap feature for NIC. In order to do this, open a Terminal and type
defaults write com.yourcompany.NIC NSAppSleepDisabled -bool YES
Later versions of NIC will fix this transparently.
Another common problem in Mac is that sometimes the device is not recognized in NIC, but when you go to the Bluetooth configuration you can see that the device connects and disconnects continuously, or it appears under the name "WT12-A". If this happens, follow these steps:
1- Turn off Enobio/Starstim off
2- Close NIC
3-Disable the Bluetooth
4-Open Finder, click Go (at the top of the screen), then click Go to Folder. Type or copy/paste /Library/Preferences and click Go. In the Preferences directory locate a file named com.apple.Bluetooth.plist and delete it.
5-Click Go again (at the top of the screen), click Go to Folder again and this time type or copy/paste ~/Library/Preferences/ByHost and click Go. In the ByHost folder locate a file that begins with com.apple.Bluetooth and delete it. This file will begin with com.apple.Bluetooth and have some random capital letters and numbers at the end.
6-Turn on Bluetooth