Ph pen calibration fails

[hello]

I have three Hanna ph testers. Only one works calibrated.
The other two won't calibrate.
I need two testers working.
The one will calibrate 7 but not 4.
The other one will show 7 but then jump to 4 and fail both.
What is a reliable dependable way to test for 6.5 ph? Are there better products? What am I doing wrong?

 

[Lil Dab]

I have three Hanna ph testers. Only one works calibrated.
The other two won't calibrate.
I need two testers working.
The one will calibrate 7 but not 4.
The other one will show 7 but then jump to 4 and fail both.
What is a reliable dependable way to test for 6.5 ph? Are there better products? What am I doing wrong?

I've been happy with my Apera meter PH60 . Sounds like your probe is messed up or bad. You could always try a liquid ph test kit not as accurate but doesn't need calibration

 

[BII]

I have three Hanna ph testers. Only one works calibrated.
The other two won't calibrate.
I need two testers working.
The one will calibrate 7 but not 4.
The other one will show 7 but then jump to 4 and fail both.
What is a reliable dependable way to test for 6.5 ph? Are there better products? What am I doing wrong?

If you haven't been taking care of the electrodes, including using a proper storage solution, they likely have gone bad (or will sooner or later).