PH pen Storage Solution??

[rastaman79]

I always just put some H20 in the cap at a pH of 7.0. Works like a charm on my Truncheon.

mine says i have to keep some 7.0ph buffer in the cap to keep it calibrated,then next time u turn it on you know its working as its reading 7.0,i change the buffer in the cap about every 5 day to stop it diluting(after rinsing off the nute solution)