Yes, they are. That’s the reason why measure circuit has to be galvanically separated. I have both EC and pH done this way. The black block is a DC-DC charge pump(converter), like this one.
OK, let’s do some summary:
Shield - 115,-
https://www.atlas-scientific.com/product_pages/components/tentacle-shield.html
pH module+probe - 149,-
https://www.atlas-scientific.com/product_pages/kits/ph-kit.html
EC module+probe 217,-
https://www.atlas-scientific.com/product_pages/kits/ec_k0_1_kit.html
EtherMega 119,-
Summary:
600,- USD
WOW! That’s a huge investment for me, when I consider that comes with no code and not assembled (power source, box, etc.). For that money I can build Growduino with four sockets(relays) and full set of sensors (also with CO2), internal UPS and all the code finished with integrated webserver- AllInOne.
But OK, I understand the principle - to develop a prototype and then in the second stage of a “project” to lower the costs for next production.
About “Chinese build quality” - I’ve compared italian and chinese Arduinos and ethernet shields many times and there is no diference in quality, stability, even in return rates.