The liquid junction of your meter's electrodes should be cleaned once a day or at least once a week to prevent clogging and to maintain accuracy.
Immerse the electrode in Hanna Cleaning Solution for about 5 minutes to eliminate all kinds of dirt and deposits from the electrode.
This will ensure correct measurements.
Hanna Cleaning Solution is available in 20 ml sachets for single-time usage or in a 230 ml bottle.
The 20 ml sachets come in a case of 25.