Review on Blue Upgrade LED Water Quality Test Meter - Pancellent TDS PH EC Temperature 4 in 1 Kit by Karen Perez

Calibration does not work as instructed. You can't do a quick tap to determine what pH solution you're using like the instructions say. It attempts to determine the solution status automatically. First, like I said, I did 6.86 and it's calibrated to 4.01. Then I did 4.01 and it doesn't calibrate at all as now it thinks 4.01 is like 2.0 so it just throws an error. From that point on, you're out of luck. A solution of 9.18 is calibrated to 6.86. You could probably fix this if the device actually works as the instructions say it does, but it doesn't. Now it's a useless heap of junk that can't be calibrated. Straight into the trash can.