Yes, of course, Hero. Your first link, I think it was, was to a 'sensor,' or probe. I thought it was a pretty good deal, too.
You might be able to buy a pH sensor module with in-built drive electronics speciffically designed for industiral control purposes that outputs a voltage (say 0 to 10V) proportional to the pH.
Yes, and they tend to be quite expensive, which is why it is so much more fun to build yourself!
Also, building your own circuit is some good time working with op amps, which can be as intriguing as microcontrollers are. As well as using an op amp to scale your pH, it is also an opportunity to get some experience with an NTC thermistor, and how to linearize, and scale that.
I haven't checked but I'd assume that the commercial pH meters have built-in temperature compensation.
Yes, I think you are right on this one. But like I say, it is a great project, really worth doing.
He, he, this always scares me:
No prices are shown but they do look expensive.
I think the ones I got were pretty good, but then I'm no expert. One of them was made in Canada, and they are both on the way to Canada, along with most of my toys. I'll sure miss being here, where one can go shopping in 'electronics dreamland,' and find many exciting things. (Not to mention the fun of dealing on them, in a language I'm not good at.)