hello. I have a calibration problem on a staline PH device: When that I

Good morning

I have a calibration problem on a staline PH device: When I put the probe in the PH 4 OK PH7 OK then the device then indicates ERROR. What do you think? THANKS

Try this little test: https://ph-redox-pool.com/gb/content/16-ma-sonde-ph-est-elle-hors-service-

Ok, because to date it indicates 8.2 and injects PH - permanently. while the manual test rather indicates 6.5!

If you add vinegar to the water does the displayed ph value drop?

I will try, thank you and have a nice day

Good day