MEA 1060 system pre-amplifier and electrode grounding

Hi,
I am using for the very first time the MEA1060-inv-BC system and I'd like to ask you a question in order to better understand its functioning.

I would really be grateful if you could provide me a brief explanation about the aim of electrode grounding. I use electrode 15 as the ground. Does this means that it is connected to the ground of the MEA system and so i should see a null voltage at electrode 15? what is it useful for?
or it means that it is used as a reference electrode, in order to perform a differential amplification in the MEA platform to reduce noise? Are the pre-amplifiers (gain about 50) embedded in the MEA platform differential amplifiers?

thank you for your kind attention
best regards

Giulia

Good Morning Guilia,

I think we have to distinguish between two things: 1.) Ground a recording electrode and 2.) use of Internal reference electrode.

In some cases you will run into situations where one or more of the recording electrodes are damaged and pick up higher levels of noise. These electrodes can be grounded and will after grounding just display amplifier noise level - but no electrode noise level. So a typical 30um diameter electrode should have 2-5uV noise when grounded and 5-15 uV when recording.

The second case is the use of Electrode 15. If you are using MEA chips with an internal reference electrode, this internal reference need to be conected with the amplifier. To do so on the MEA1060 BC amplifier you connect the iR via El15 with the housing ground of the MEA1060BC. The voltage on El15 will not be precisely zero, but still show the amplifier noise, but no biological signals. If you need to obtain signals from El15 or your MEA is not equipped with an internal reference (iR) you can ground the bath via an Ag/AgCl pellet and measure potential difference between the pellet and the recording electrodes.

I hope that answered your questions...

Greetings

Thomas

Dear Thomas,
thank yuou for your reply...but i still have a doubt. I thought that the reference electrode could serve as reference input to differential amplifiers, in order to cancel the common noise shared by every electrode and electrode 15. So, is that wrong?
thank you!

Hi Giulia,

this is not really working, as the noise on the reference is smaller.
Normally you should not run into any issues with 50Hz noise as the housing shields very well.
If you cannot remove the noise by shielding 6 grounding, you can use the channel tool in MC_Rack in order to subtract one channel reflecting just the noise, but no biological signal. Please just check the help function of MC_Rack for details on the "Channel Tool".

Greetings

Thomas