Review on IPower LGTESTWATERTDSV1 Professional Temperature Hydroponics by Marcel Robinson

Cannot calibrate any of these meters. I have been using them for 15 years and bought 2 Ph pens because the price was low. The Ph knobs cannot be calibrated because the knobs are so far away that they cannot be calibrated. They don't include 9.18ph calibration powder so you can't get an accurate three way calibration, but even if you have the correct calibration powder the pen is so far from accurate that you can't get it to to recognize the right body. Cheap pens, but they belong in the trash. Both ph pens I bought are the same so this seller is probably just selling broken ph pens for cheap.