Hanna pH tester problem
I recently attempted to upgrade from litmus paper to a meter for pH testing, but I'm having some trouble. I bought a HANNA 98108 pHep+.
I strictly followed all package instructions upon opening it, including letting it sit in pH 7.01 solution for 2 hours to activate the electrode.
However, it seems impossible to calibrate. After calibrating with 7.01 and 4.01 solution, within a minute it is off again, generally by a lot. When compared with the results of litmus paper, it is usually off by at least a full point immediately after calibration, but it varies greatly. When left to sit in 7.01 calibration solution, the reading slowly slides until after several minutes it may be up or down several points.
Am I missing something? Did I just get a bad unit?