Before shipment, the factory adds in some water droplets to the tester's cap to maintain a hydrated atmosphere for the probe. This ensures that the pH sensor keeps its sensitivity. Therefore, users can begin using their tester immediately upon receiving it. 

This practice of adding several drops of water into the cap is highly recommended for frequent users when storing the tester. However, if the tester has not been used in a long time (eg > 1 month) users should soak it in 3M KCL solution overnight to recover its sensitivity.