potentiostat using op-amp's

[sukhavsa]

Hi all

I am working on a project to build the electronic interface for an electrochemical cell.
It is a three electrode system. Now i have to build a potentiostat for it. After doing some reading i found the following circuit.

I wired the circuit but the output of op2 remains constant at -4.43v while i change vin and even when in did not apply any input.

please help me analyze the circuit, and i am not even quite sure how to test it.

any suggestions would be really helpful.

thanks [/img]

 

[LvW]

Without any negative feedback opamp2 has no fixed operating point and is, instead, in saturation (somewhat below the power rail voltage).

 

[sukhavsa]

I guess there will be a feedback when the electrochemical cell is included.

Sorry for not mentioning it before.
here is the circuit including the equivalent circuit of the electro chemical cell.[/img]

 

[LvW]

I guess there will be a feedback when the electrochemical cell is included.
.......

And what about the supply? Dual or single?
And - please give resistor values.

 

[FvM]

I guess there will be a feedback when the electrochemical cell is included.

Right in principle, but additional frequency compensation respectively I or PI feedback charateristic may be required
for stable operation because the OP open loop gain is possibly too high.

You can refer to electrochemical sensor application literature for practical potentiostate circuits, e.g.:

 

[Dr_J]

Hi sukhavsa,

did you have any success building your potentiostat?

I am attempting to build a potentiostat to supply up to +/-5V at max. 200mA, and am having some frustration! Would love some information if you have had some success, can you please update the post?

 

[chazziemann]

Hi sukhavsa,

did you have any success building your potentiostat?

I am attempting to build a potentiostat to supply up to +/-5V at max. 200mA, and am having some frustration! Would love some information if you have had some success, can you please update the post?

Hi Dr-J

how did you get on with the project?. I too am trying to work on one aswell, very frustrating when you dont know!!