ph meter

Hi all,


I have a milwaukee mw 100 ph meter and I'm not sure if its working right


I cleaned and calibrated the meter, but still the same problem


It can read the calibration solution with no problems, if I use the 7.0 solution, it shows 7.0 and the same for the 4.0 solution



If I make a nutrient solution with ph 5.8, the ph drops after 30 min to 5.5, if I stir the water, he goes back to 5.8, if I dont move the electrode it goes down to 5.5, stiring and it jumps to 5.8


What do you think? Should I buy a new one?


The meter has a accuracy of + - 0.2


Greetings

That is as accurate as you will get with a cheap meter. I recommend useing a colorimetric test kit (pH drops not paper) to cross reference. You sound like your on top of the storage and calibration.
Introducing air eg stirring will effect the reading