... 4.Calibration: 1point PH-107 Pocket-sized ph meter Feature: This is an economic type ph meter with high precision ... design and high sensitivity. Very convenient to test ph value for lab and industry and other aspects, ... compensated for temperature variations.• After use, switch off pH meter, use the water clean the electrode and ... screwing back the ring. High-accuracy!! PH-107 Pocket-sized ph meter