This is why I needed an op amp: LM35 Temperature Sensor
Yeah if you want low cost reliable sensors, you go 5 volt, technology really hasn’t changed when it come to using a split core sensor lol. But I see your point: Use more expensive sensors or switch back to an arduino with a gsm shield.
I will have to disagree on the arduino not for real projects. Thanks also for the link to that thread, reading it now.