does anybody know how you can create a constant cathodic voltage (+/- 0 mV SHE) or a constant current ranging from 1 up to 200 mA. The electron supply should not vary too much. I know a potentiostat can do the job, but it's too expensive. I assume that the high cost for a potentiostat is because it's very precise. Do there exist cheaper systems which can do either one of the jobs (or the two) with an accuracy (standard deviation) of +/- 5 mV (for constant potential) or +/- 0,5 mA (for constant current)?
Sure. Someone wanted to fly a potentiostat in a satellite experiment, and got the Nijmegen (now Radboud) University to build them a potentiostat on a printed circuit board. It didn't have any heavy expensive poteniometers, because it was a single purpose device.
In order to make a fairly trivial job more interesting, I made the design more or less indestructible - you could put 240V AC across any of the inputs and they wouldn't blow up - and it still wasn't all that expensive. The bare printed circuit board was the most expensive component.
Commercial potentiostats are expensive largely because the market is tiny, and every machine has to make an enormous profit to keep the manufactueres in business. It pays to build them like tanks and fit them with best and biggest potentiometers money can buy, because the extra cost doesn't make much difference to price to the customer, and the extra quality can squeeze out cheaper-looking competition.
E-mail me with more detail about your application (billDOTslomanATieeePOINTorg), and I'll see if I can find the circuit diagram and work out a way of sending you a copy.
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