Page 1 of 1

noise level at electrodes immersed in water

Posted: Thu Sep 27, 2007 11:06 am
by eltsianaka
Hi!

I had recently some high values during some measurements and I tested the system with the electrodes immersed in water to see if everything is ok. I had a value range of 2uV up to74uV. (The offset values of the electrodes were under +-30mV.)
Is it reasonable to get such values? Do you think that this is due to electromagnetic noise?

Thanks!

Posted: Thu Sep 27, 2007 4:39 pm
by Coen
Noise should be below 10-20 uV peak-to-peak (0.1 - 100 Hz bandwidth).

- the pellets have to soak for 5-10 minutes before noise and offsets have stabilized to low values.
- use a sufficient amount of salt in the water (without salt, higher noise levels may be encountered), ras a rule of the thump use a spoon of salt per liter water
- use the "referenced" display mode to reject Common Mode noise
- bundle the cables to eliminate magnetic interference

Best regards, Coen (BioSemi)