Review on High Accuracy Digital Water Tester Pen – pH Meter with 0-14 pH Measurement Range for Drinking Water, Plants, and Swimming Pools - Yellow by Amber Perry

The pH meter did not work from the start. The readings for every solution I tested, from diluted baking soda (mild lye) to diluted vinegar, all readings were around 11.1-11.3 (strongly alkaline pH, which is rare). There is no point in calibrating a device that is insensitive to changes in acidity. Most likely some liquid contacts will clog if stored dry. For most pH electrodes it is recommended to store them in a buffer solution; Leaving glass electrodes dry for months will kill them. This most likely happened with this particular pH meter. I sent it back for a full refund - and received it quickly from Revain (thanks!).