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Are electrodes mostly homogeneous or are there variations by usage? My main usage is EEG. I have some interests in other areas and see similar electrodes sold for less money when marketed for different purposes.

I imagine there are differences in precision? Is that accurate or

Sorry for the basic question.

I've been experimenting with the use of electrodes for EEG and I'm trying to understand if these expensive EEG electrodes ordered from the EEG development board makers are "special" in some way that I'm not aware of - such as if different hardware designs detect different ranges of electrical activity - or if all electrodes styled for use on humans result in essentially the same data and just perhaps vary by accuracy?

Are there common metrics or features used to rate or distinguish electrodes by purpose?

Stated differently, my question is essentially what factors to consider when selecting an electrode for human use, such as EEG, ECG/EKG, EMG, etc.

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Biopotential electrodes are often nonpolarizable, meaning that they conduct current well without a blocking capacitance. To do this, there is usually a layer of a metal covered with a salt of that metal, most often silver-silver chloride.

The practice gives you the best frequency response and the least distortion of the signal you're trying to measure.

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Electrodes can be different in shape, depending on their purpose. For example, EEG electrodes tend to be cup-shaped. The cup can then hold some conductive paste, improving signal-to-noise ratio. ECG electrodes on the other hand tend to be patches that can be used on larger surfaces, such as the chest. The conductive material is then mixed with the sticky layer. EMG electrodes tend to be similar to ECG electrodes, if not the same.

That's for "wet" electrodes. Now on to dry electrodes. These use different ways to conduct signals. Some require you to apply a conductive paste for increased signal-to-noise ratio. Others have a pin-like structure that pokes into the upper skin layer. They can come in a variety of shapes and sizes, all meant for improving signal-to-noise ratio (and all of course claiming they're the best). And again others are simple metal surfaces that can be attached to conductive materials of your own choosing. The latter can be found in the increasingly popular ECG chest straps for athletes.

And last but not least, there's the active electrode. These electrodes have tiny circuits in them that amplify the signal and filter out common noise. These can be seen below. Perhaps the "special" electrodes are active ones?

Active electrode.

As far as materials go, there's not much difference really. Some are slightly better than others at transporting signals, but unless you're ordering from China, you can rest assured most electrodes will conduct the signals they are intended to conduct.

Real question is, what are you wanting to use your electrodes for?

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  • \$\begingroup\$ Hi, thanks so much. You're right, I already use both dry and wet electrodes of different shapes. This is for human use, such as EEG, ECG/EKG, EMG, etc. \$\endgroup\$ – Hack-R Dec 20 '18 at 17:57
  • \$\begingroup\$ EEG tends to do better with a different type of electrodes than ECG and EMG. Remember that you're trying to stick the electrodes on a specific type of surface and the contact with that surface, has a major influence on the quality of the returning signal. E.g.: ECG and EMG go on large surface areas, whereas EEG electrodes are usually attached to the head using some sort of helmet or net. With that being said (and going back to your original question), if the electrode is designed specifically for your application (for example EEG), any electrode will do. \$\endgroup\$ – user207636 Dec 21 '18 at 14:26
  • \$\begingroup\$ Thank you that helps. What would be great is if I could list the ways that they are different, so that I can understand fully and reference it. I can use some of what you mentioned. \$\endgroup\$ – Hack-R Dec 21 '18 at 14:40

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