Digital pH meters need some care and attention.
A little effort will keep them in good shape, which will enhance and ensure their accuracy and extend their useful life.
This solution can be used to store pH electrodes when not is use.
Basically the electrode (glass bulb) at the end of the meter should be placed completely in the solution.
This will condition the probe and maximize its useful life. The same solution can be used for refilling the probes on certain meters.