I agree with William. We at Florida Research Instruments have done a lot of work on Active Dry Electrodes but a very good signal can be obtained with a proper electrode and short lead wires. We offer EEG Dry Electrodes and 18 inch lead wires. See www.FRI-FL.com click on the Product Tab and EEG Electrodes.
I've learned that Cognionics is now selling their dry flex sensors for $40 each, or $15/sensor in quantities greater than 100: http://cognionics.com/index.php/products/sensors/flex Cognionics sensors were successfully used with OpenBCI in a recent exploratorium exhibit:
I've been trying to get a hold of Mr. Karl Zurn from FRI but I was not able to succeed at it. Their company contact information is no good either, they're not picking up the phone, always redirecting to the voice mail.
I ordered the Disposable / Reusable Dry Electrodes from http://fri-fl-shop.com one month ago. So far, I still did not get the order. even I checked USPS, it said that it is still in U.S. I have no choice but to pay another $50 for DHL delivery to resend the order.
Frankly, I am very dispointed disappointed with fri-fi' delivery compartner.
Afliu's problem is with China Post that can take 4 weeks plus. The other options are FedEx, UPS or DHL these cost about $65 we agreed to resend at $50 (below our cost).
Some people have had questions about our EEG Dry Electrodes. I have post some answers on our web site www.fri-fl.com click on the Manual Tab and look at EEG Electrode Information.
Let me be clear, I did not complain DHL $50 delivery fee. Even, I would select DHL if I knew USPS is so slow at the very begining. I mean DHL and Fedex are alwasy fast. Even it will only take 1 week to deliver good from U.S to China.
By the way, I post the message here beause I just saw trungnv has the same order experience.
I do not have much experience with wear on the comb end of our electrodes because the snap end will fail much before the comb end. I would assume William’s experience with the electrodes he uses would be the same as ours on the comb end.
On another topic I think it is a big benefit that you can inject gel in the hole in the top of the electrode. I can see someone with a 64 channel headset having a few bad connections on a person with a lot of hair. It is rather easy to inject some electrode gel to fix the connection. I can see a researcher being a bit irritated when he/she spent the time and money to pay, setup and run a subject now having to throw out the data because of bad connections. Our leads allow you to inject gel after the electrodes are in place.
The cost of throwing away our electrodes after 10-20 uses is 3 to 6 cents per application. Compared to the re-chlorinating a silver cup electrode is small.
Using the Dritz snap is a good inexpensive way to attach to our electrodes
Here's a paper just published October 2015 on the Versus dry/active headset. Conductive carbon-silicon sensors at Fz Pz C3 Cz C4. Headset is incorporated into a pair of stereo around-the-ear headphones. Wireless.
Validation of a wireless dry electrode system for electroencephalography
Methods
In this investigation the validity of a wireless dry electrode system compared to a conventional wet electrode system was assessed, while addressing methodological limitations. In Experiment 1, the signal output of both EEG systems was examined at Fz, C3, Cz, C4, and Pz using a conductive head model and generated test signals at 2.5 Hz, 10 Hz, and 39 Hz. In Experiment 2, two-minutes of eyes-closed and eyes-open EEG data was recorded simultaneously with both devices from the adjacent electrode sites in a sample of healthy adults.
Results
Between group effects and frequency*device and electrode*device interactions were assessed using a mixed ANOVA for the simulated and in vivo signal output, producing no significant effects . Bivariate correlation coefficients were calculated to assess the relationship between electrode pairs during the simultaneous in vivo recordings, indicating a significant positive relationship (all p's < .05) and larger correlation coefficients (r > ±0.5) between the dry and wet electrode signal amplitude were observed for theta, alpha, beta 1, beta 2, beta 3, and gamma in both the eyes-closed and eyes-open conditions.
Joel, Our connectors are gold plated. I have not noticed corrosion. We have some snapped for several months but these are just sitting on the shelf. I wonder if the issue on yours is moisture.
Our electrodes are plated with AG AG-CL.
William, I would think the main limitation is the number of time the snap is taken on and off. We do not normally use a gel or saline solution this might limit the use on the comb end.
I would think the best solution for the OpenBCI headsets would be to use the Dritz snap.
Regarding the Dritz snap - could someone please outline exactly how the electrode (presumably from FRI) are connected to them and how the aggregate is connected to Velcro.
I didn't understand why BOTH 10 and 4 mm snaps are needed and WHAT parts are soldered and for what purpose.
Showing the FRI comb plugged into a Dritz snap #10, which is in turn soldered to a Dritz #4 to then plug into a standard ECG / EEG female snap electrode lead wire.
This is not necessary if you use the components from FRI directly. Using those components you would use the velcro straps with holes to position your comb, then clip on with the FRI spring loaded electrode wire.
The only advantage of the Dritz #10 is that it can be assembled into other configurations if you want to have "snap-in" FRI combs. If you are using velcro it is NOT what you want.
The whole subject of the Dritz #10 female snap came up recently in the context of how the FRI combs could snap into the Ultracortex IV. However the Dritz #10 is rather bulky both in diameter and depth of the molded hole. So it might not be so practical, given the current electrode holder dimensions.
By changing the ways the nuts and lockwashers are utilized in the electrode holders, it is possible to be able to remove and attach new FRI combs or tDCS pads to the electrode holders. This is documented on the Feedback thread,
Here's a recent price quote from Cognionics on their dry sensor headset. It was posted on another forum that I follow.
----
Thank you very much for your inquiry. The wireless, dry Quick-20 can be configured with anywhere from 2 to a full complement of the 20 positions of a standard 10-20 montage, plus ground. Pricing depends on channel count and other options and features. A standard, fully populated 10-20 costs $14,600. A 2 channel version costs $2,250, and other channel counts would be in between.
Prices are for complete systems, including headset, wireless amplifier and electronics, software, extra dry sensors, supplies, and video training via Skype. Channel count is in addition to 3 channels of continuous accelerometer readings for x, y and z motion.
Key features:
Dry Electrodes with Active Pre-Amplification and Shielding for best possible signal quality
24-bit High Resolution Digitizer which greatly reduces signal loss after motion
Custom High-Speed Wireless Transmitter which mostly eliminates Bluetooth Pairing problems
No adjustments - supports head sizes 50 cm to 63 cm. Child size headsets available
Low Operating Cost - Sensors Last an Average of More than 250 uses
Live Installation and Training via Televideo
Carrying Case with Foam Inserts
If you are interested in research, the system provides access to the raw data, along with various interfaces to access the raw data. Software includes data acquisition, display, storage, live impedance check, and scripts to import to Matlab, Open Vibe, EEGLab, LSL, Neuroguide and PyCorder. We provide full documentation on the unfiltered data stream and we can provide you with sample source code in Java or C# if you want to port the software to another operating system (e.g., Android or IOS).
We also offer a variety of other options if you need to integrate other devices or collect other physiological data (e.g., ECG or Respiration).
Again, thank you for your interest and we would be happy to answer any other questions.
Conor and Joel did some earlier tests in this thread with sensors printed from conductive filament. However that filament was considerably higher in resistance than this new one:
Just ran across this graphene based filament, .6 ohms-cm.
I don't think it should have a DC offset as it is non metallic? If you view some of the earlier posts in this thread you can see a variety of conductive polymer combs, some rubber. In their tests Conor was able to get decent EEG with the higher resistance material by adding gel. This should need no gel.
The IMEC comb (conductive rubber), needed an active amp circuit behind it. Likely because of the higher resistance. Graphene polymer combs should operate in a passive mode.
Now they may not be as good as Ag-AgCl, that is considered the king of the hill as far as skin sensors. But the potential advantage of polymer would be the custom shapes and ability to flex.
Here is David's @ratlabguy ARL report on their conductive dry sensors, similar idea. They get decent passive results. They use carbon nanofiber doped elastomer. The graphene doped material should be even lower resistance since those are sheet-like inclusions vs. rods.
Cool paper. We tried (and did) use doped silicones...but their addition of a lubricant to help the mixing process was something that we didn't consider. I'm not familiar at all with the implications of adding such a lubricant, but it sure did seem to work out for them. Very cool.
Also, nice use of head phantoms. Their such helpful devices.
We have been using dry Ag-AgCl electrodes for our experiments and they have been working great with OpenBCI. But we have been wanting to use a more "robust" material, like Gold, for repeated use. Has anyone worked with gold or other materials to do a good comparison for EEG measurements?
The Ag-AgCl electrodes are considered the best for biopotential measurements; even superior to gold. Both types have a base metal (silver or tin) plated with AgCl or gold. So depending on the plating thickness, can have variable durability / lifetime. Here's a paper contrasting various electrode metal types,
Thanks. These are great resources! I'm curious if its affects the experiment by using Ag-AgCl electrode as a ground when comparing other electrodes as used in the paper below.
Generally in EEG it's advisable to use electrodes all of the same metal type (the head electrodes, references, ground). This is to avoid potential 'battery' effects. However in some situations I've seen Ag-AgCl grounds and references mixed in with gold cup electrodes on the head. That combination is apparently safe to use. (Assuming you are not doing infra slow EEG.)
Good point but using Ag AgCl is the best in all cases. But if you used Gold and Ag AgCl I think it would be better than A gold gold. When you have an offset drift in a gold gold there is no guarantee it would in the same direction.
Comments
I agree with William.
We at Florida Research Instruments have done a lot of work on Active Dry
Electrodes but a very good signal can be obtained with a proper electrode and
short lead wires. We offer EEG Dry
Electrodes and 18 inch lead wires. See www.FRI-FL.com click on the Product Tab and
EEG Electrodes.
Karl Zurn
Thank you
Bests,
Svato
See @kartik_subbarao 's post from March in this search result,
http://www.openbci.com/forum/index.php?p=/search&Search=cognionics
$40 each, or $15/sensor in quantities greater than 100:
http://cognionics.com/index.php/products/sensors/flex
Cognionics sensors were successfully used with OpenBCI in a recent exploratorium exhibit:
http://openbci.com/forum/index.php?p=/discussion/319/cognitive-technologies-maker-expo-at-sf-exploratorium
William
Frankly, I am very dispointed disappointed with fri-fi' delivery compartner.
Let me be clear, I did not complain DHL $50 delivery fee. Even, I would select DHL if I knew USPS is so slow at the very begining. I mean DHL and Fedex are alwasy fast. Even it will only take 1 week to deliver good from U.S to China.
By the way, I post the message here beause I just saw trungnv has the same order experience.
Again, thanks for the discount for DHL delivery .
Regards,
-Anfeng
I do not have much experience with wear on the comb end of our electrodes because the snap end will fail much before the comb end. I would assume William’s experience with the electrodes he uses would be the same as ours on the comb end.
On another topic I think it is a big benefit that you can inject gel in the hole in the top of the electrode. I can see someone with a 64 channel headset having a few bad connections on a person with a lot of hair. It is rather easy to inject some electrode gel to fix the connection. I can see a researcher being a bit irritated when he/she spent the time and money to pay, setup and run a subject now having to throw out the data because of bad connections. Our leads allow you to inject gel after the electrodes are in place.
The cost of throwing away our electrodes after 10-20 uses is 3 to 6 cents per application. Compared to the re-chlorinating a silver cup electrode is small.
Using the Dritz snap is a good inexpensive way to attach to our electrodes
Karl Zurn, FRI www.fri-fl.com
Validation of a wireless dry electrode system for electroencephalography
Methods
In this investigation the validity of a wireless dry electrode system compared to a conventional wet electrode system was assessed, while addressing methodological limitations. In Experiment 1, the signal output of both EEG systems was examined at Fz, C3, Cz, C4, and Pz using a conductive head model and generated test signals at 2.5 Hz, 10 Hz, and 39 Hz. In Experiment 2, two-minutes of eyes-closed and eyes-open EEG data was recorded simultaneously with both devices from the adjacent electrode sites in a sample of healthy adults.
Results
Between group effects and frequency*device and electrode*device interactions were assessed using a mixed ANOVA for the simulated and in vivo signal output, producing no significant effects . Bivariate correlation coefficients were calculated to assess the relationship between electrode pairs during the simultaneous in vivo recordings, indicating a significant positive relationship (all p's < .05) and larger correlation coefficients (r > ±0.5) between the dry and wet electrode signal amplitude were observed for theta, alpha, beta 1, beta 2, beta 3, and gamma in both the eyes-closed and eyes-open conditions.
Joel and William,
Joel, Our connectors are gold plated. I have not noticed corrosion. We have some snapped for several months but
these are just sitting on the shelf. I
wonder if the issue on yours is moisture.
Our electrodes are plated with AG AG-CL.
William, I would think the main limitation is the number
of time the snap is taken on and off. We
do not normally use a gel or saline solution this might limit the use on the
comb end.
I would think the best solution for the OpenBCI
headsets would be to use the Dritz snap.
Karl
If the 10 female is soldered to a 4 male snap pin, it can plug into the female snap on ECG leads.
By changing the ways the nuts and lockwashers are utilized in the electrode holders, it is possible to be able to remove and attach new FRI combs or tDCS pads to the electrode holders. This is documented on the Feedback thread,
http://openbci.com/forum/index.php?p=/discussion/541/ultracortex-mark-iii-feedback-mark-iv-priorities
There may also be other sockets which mate with the FRI combs, we have not looked around extensively.
http://phys.org/news/2016-01-brain-lab.html
http://www.cognionics.com/
http://qusp.io/
http://qusp.io/projects/
NeuroScale and NeuroPype
http://neuroscale.io/
http://neuropype.io/
William
----
Thank you very much for your inquiry. The wireless, dry Quick-20 can be configured with anywhere from 2 to a full complement of the 20 positions of a standard 10-20 montage, plus ground. Pricing depends on channel count and other options and features. A standard, fully populated 10-20 costs $14,600. A 2 channel version costs $2,250, and other channel counts would be in between.
Prices are for complete systems, including headset, wireless amplifier and electronics, software, extra dry sensors, supplies, and video training via Skype. Channel count is in addition to 3 channels of continuous accelerometer readings for x, y and z motion.
Key features:
If you are interested in research, the system provides access to the raw data, along with various interfaces to access the raw data. Software includes data acquisition, display, storage, live impedance check, and scripts to import to Matlab, Open Vibe, EEGLab, LSL, Neuroguide and PyCorder. We provide full documentation on the unfiltered data stream and we can provide you with sample source code in Java or C# if you want to port the software to another operating system (e.g., Android or IOS).
We also offer a variety of other options if you need to integrate other devices or collect other physiological data (e.g., ECG or Respiration).
Again, thank you for your interest and we would be happy to answer any other questions.
Best,
Cognionics, Inc.
http://bio-medical.com/products/freedom-24d-wireless-eeg-headset-w-brainavatar-acquisition-software.html
Link has a Youtube video showing application and adjustment.
http://bio-medical.com/products/dsi-24-wearable-sensing-eeg-headset-w-neuroguide-gold-bundle.html
Another version they sell includes the QEEG Neuroguide package. Not branded Brainmaster.
Just ran across this graphene based filament, .6 ohms-cm.
http://www.blackmagic3d.com/Conductive-Graphene-3D-Printing-PLA-Filament-p/grphn-175.htm
Looks like it's targeting many electronics applications, including body sensors.
An engineer on their Youtube channel even did a 555 timer LED flasher (complete with battery holder).
There is a race to the lowest ohms-cm, these guys at .75
http://functionalize.com/about/functionalize-f-electric-highly-conductive-filament/
Also this pulls up tons of other links,
https://www.google.com/search?q=3d+printing+conductive+filament+ohm-cm
A potential downside of this filament is the extra care needed in printing and storage of the filament. The first link has some of that info.
William
Evaluation of commercially available electrodes and gels for recording of slow EEG potentials
http://lib.tkk.fi/Diss/2006/isbn9512269562/article3.pdf
A comparison between gold pin, titanium, and polyurethane / titanium nitride dry electrodes,
https://www.tu-ilmenau.de/fileadmin/media/bmti/ieee_2014/Fiedler_Acta_IMEKO_2014_dry_electrodes.pdf
g.tec uses gold combs in their g.SAHARA active electrodes. Other active combs I'm aware of use conductive polymers.
https://www.google.com/search?q=eeg+electrodes+gold+pins
https://www.tu-ilmenau.de/fileadmin/media/bmti/ieee_2014/Fiedler_Acta_IMEKO_2014_dry_electrodes.pdf