I need to hook up a pH meter to Arduino. The ones sold for this purpose are all quite expensive and pH meters by their very nature have a life span of only about a year even when properly taken care of, so replacing an expensive pH meter every year will incur an ongoing cost.
There are cheap standalone pH meters that aren't meant to be hooked into anything else:
I have one and it works fine. It also has a built-in thermometer which is critical because temperature can change pH, whereas the Arduino meters don't, so I would have to buy a separate submersible temp probe, get the readings, and do the calculations of true pH in code, etc.
I'm wondering if I can open it up and get some sort of data signal from one of the pins. It also has an LCD display that shows the pH to the user, so maybe I can hook wires into the display and "read" whatever the display is showing electronically?
I actually opened my probe before I saw the post about the guy hacking his pH meter. Mine uses the same chip and I'm not going to spend that much time and effort to hack into my cheap meter. Since pH meters don't last very long even when taking care of, any meter would need to be easily replaceable every year or so. Don't what that guy did isn't it.
So I'm going to conclude that if you want a cheap pH meter, you need to either buy cheaper Arduino-compatible probes to begin with, or if you want to use really cheap standalone units, hook up some sort of camera and OCR system with a Raspberry Pi so you can read and decipher the LCD that way, because splicing into a cheap standalone meter is just going to be too much effort.
