ph meters

Havent bought one in years. Owned like 6-7 of them in the past. So i bought from a hydro store soaked it in water and then ph and 7 worked just fine . Now the 4 ph at 7. So i cant get it to read 4. Say 4 or even calibrate at 4. So i took it back. He gave me another one...

I bought this meter for $30 and I swear it doesn't work. It says 7.0 regardless of what I'm testing. Every plant i own apparently has a ph of 7 and even the outside ground is 7. My tap water is also at 7. EVERYTHING IS READING 7 Is this a busted meter or is it possible that everything i test is...

What are you guys using to measure your pH & ppm levels? BlueLab and Hannah are expensive brands but seem to be more reliable/accurate. Things like ATC (automatic temperature compensation) and accuracy are intricacies that worry me about the cheaper products (the $20-$25 pens you can find on...