I can't find my current manual, but a generic online one says this
maintaining your pH meter
If you do not look after your pH meter then incorrect measurements of pH levels may occur. As a minimum, you must always wash the pH electrode (the measuring part of the instrument) in clean water. Do not touch the pH electrode unless using a damp tissue or cloth for cleaning and then only using extreme care.
When not in use, ensure the pH meter electrode is kept moist in either storage solution or a pH 4 solution. If the sensor is allowed to dry out completely, the instrument’s performance will be effected and its warranty invalidated.
I'm pretty certain the pH meter I have now and the I owned before this said 7.01 or distilled water. Both are bench top testers.
Now I'm trying to hunt down the manual but can't find it and wasn't online that I could find.