I'm actually building my own hydroponic system to study the plant grow, and i've wanted to put an EC meter for monitoring the EC level of the water. I've found the one who has been published on Elektor website, and following the link, he bring me here

If someone can share with me the source project (Proteus i guess, i've the V8.0 version) of the EC-meter, because on the shematics published on the Elektor page, some informations are missing, for exemple, i can't see where the VEE rail go, after some retro ingeniering, i've find some pin of the TL074 on this rail but i can't find all the rail.
I need to redesign the PCB shape, because i need to put this on my main PCB.
If somebody have made some improuvement, feel free to share with me

Thanks you in advance,
Maxime