E.C. meters

The measurement of conductivity is often overlooked in aquariums, despite its undoubted utility. For lovers of DIY here are two articles that explain how to achieve a conductivity meter.
The first is at it.hobby.acquari. The circuit , though very simple to implement, has the disadvantage of requiring a PC for the measure.


The other circuit is on octiva net: it's a school project and is relatively simple and very well explained ...