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Transistor, relay or?.. for science experiment

Dear forum

I am a researcher with the technical university of Denmark, my field is environmental engineering .

I am carrying out experiments to clean surface water sediments using bio-electrodes.
For this purpose I have assembled a data logger from basic arduino and breakout boards etc.
I am measuring voltage between 2 electrodes in comparison pairs, using ads1115's
Voltages are <1V (most of the time ca 0.0001-0.1V) at <2mA

I want to add the functionality to through code, break/open the circuit at a timing I choose (e.g. 1 time every day) in order to automatically measure open circuit potential, for 15 minutes and then close/reconnect the circuit again.

Open circuit potential I expect in the range of 0.3-0.8V

For this I as planning to use relays, but figure that might be overkill, and would consider using transistors.

It is important that I loose as little signal as possible when measuring.

I am a bit out of my field here, so I would greatly appreciate input :)

best regards
Karl
 

Harald Kapp

Moderator
Moderator
Transistors are no good at switching these extremely low voltage levels. Even standard relays will not work reliably. Mercury wetted relays may be suitable.
A better option, imho, is to amplify the signal and switch the amplified signal. If that is not possible, use the wetted relays.
 

Harald Kapp

Moderator
Moderator
You can't switch 0.0001-0.1V and expect reasonable measured values.
Sorry for being not really precise, the idea didn't find the way from head to keyboard: of course you can, but not using transistors. Use a wetted relay or amplify first, then switch. Or use an amplifier that can be turned on and off.
 
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