Review on Rechargeable Digital Water pH Meter with ATC - High Precision 0.01pH Resolution Tester for Hydroponics, Aquarium, and Lab - Measurement Range 0~14 pH by Bryce Marshall

We were a bit disappointed with this counter, so I decided to calibrate it. Big mistake. It randomly picks the wrong point to calibrate. In a buffer with a pH of 6.86, he usually chooses a value of 9.18. In a pH buffer of 4.01, he usually chooses 6.86, but sometimes 9.18. From time to time one of the calibration points gets correct, but then when I try to calibrate pH 4.01 it distorts the whole calibration curve. I compare it to a pH 7.00 reference solution and get 7.34. The counter can no longer be used. Edit: I was able to fix this problem. I immersed the end of the probe in a saturated solution of potassium chloride for a few hours. Thoroughly flushed and was able to properly calibrate the meter. After all, it correctly passed the test with a pH 7.0 reference solution. They state that the electrode does not require a storage solution but will deteriorate if not stored in KCl. I suspect some of the other reviews mentioning calibration issues are suffering from the same issue.