What to choose for Open&Close a circuit.

Hello, Im doing a project which involves reading a differential voltage produced by two electrodes of a fuel cell connected by an external resistance. Currently im measuring differential voltage with ads1115 and using 1000 Ohm as fixed external resistance. The voltage across the resistance is less than 1V and sometimes become negative (see attachments). The current produced by the fuel cell is less than 1 mA.

I want to change the fixed external resistance of 1000 ohm using a digipot (ad5254 10k) on 4 similar fuel cells. Every hour I need to disconnect the digipots (open the circuit to set an infinite resistance between electrodes), read the voltages, make some calculations to get new external resistance values for the 4 cells, and connect again the digipots (the digipot remains disconnected for around half of a second). I have read that i need some kind of relay, but im not sure which one will be convenient for my project so I will appreciate any help. Thanks.

At least the ADS5124/5144 have a shutdown mode that disconnects the wiper. This may or may not help, depending on the remaining connections between the fuel cells.

want to change the fixed external resistance of 1000 ohm using a digipot (ad5254 10k) on 4 similar fuel cells.

Check how much current that digipot can take, you might be supprised at how small it is.

Maximum current is 5mA for AD5254 and 6mA for AD5144A so i think its ok. I checked the shutdown mode of AD5144A and it says terminal A is open circuited and terminal B is connected to terminal W. So i will need to connect one electrode to terminal A ,the other to terminal W and when i need to open the circuit just enter the shutdown mode right? that way i don't have to buy any relay?

Yes, that's the plan. Please note that shutdown applies to all channels at once, but this should not be a problem.

Maximum current is 5mA for AD5254 and 6mA for AD5144A so i think its ok.

So the voltage between the cells is not going to be more that 1V then?

Grumpy_Mike:
So the voltage between the cells is not going to be more that 1V then?

No, these are fuel cells powered by bacteria so the voltage is quite low, I expect a maximum of 0.8V on open circuit and on 0.2 V on average in closed circuit for each cell.

DrDiettrich:
Yes, that's the plan. Please note that shutdown applies to all channels at once, but this should not be a problem.

Nothing wrong indeed.

No, these are fuel cells powered by bacteria so the voltage is quite low,

So you actually mean yes they are not going to be above 1V.

It would have been good to know that at the start rather than drip feeding information.

He already wrote at the thread start:

DiegoCarva:
The voltage across the resistance is less than 1V and sometimes become negative (see attachments). The current produced by the fuel cell is less than 1 mA.