I guess this is more of a review request than a specific question, but I was wondering if anyone has any experience with electrochemical sensors and the required circuits for gaining accurate measurements from them. Even if it's not specific to this particular use case, any general circuit criticism would be greatly appreciated.
The idea is to be able to monitor carbon monoxide and nitrogen dioxide (not at the same time) in a single unit. From the research that I have, they appear to be particularly sensitive to noise and getting accurate measurements means ensuring the circuit is as stable as possible with any potential noise from power supplies and the outside world kept as low as possible.
Although the power supply with be some form of 12V DC adaptor, I have tried to incorporate enough filtering to limit the chance of any ripple or supply spikes. The DC bridge is to eliminate the possibility of reverse polarity, but also nice to have that it will still operate with a reversed polarity input.
A battery backup is needed for biased cells, as they don't like being unpowered. This unit should always be powered, but on the chance someone turns the plug off, it will remain on.
The potentiostat and measurement circuits are widely available, and all very much similar. These are mostly copied with some small changes of values and such to suit my needs.
The outputs will be read by a PC and the cards datasheet claims an approximate 100 Gigaohm input impedance, so the 100 ohm resistor should cause minimum drop across it, but allows the use of a zener to protect measurement card in case of any issues. The 10uF output filtering was chosen based on the fact that 10uF caps are already present in the circuit and should provide a suitable enough LPF.
As I said, any criticisms or feedback would be greatly appreciated. This is a project for work, but I am also currently on a HND and am using this as a bit of a learning tool and being new to design means that although I think this is mostly good to go, I may be missing something obvious that a more experienced eye may be able to help with.
