Review on Digital Meter Drinking Hydroponics Aquarium by Keith Alvord

The pH pen in this kit is junk. At first it got stuck reading all zeros. After playing around with it for a while it seems to be behaving normally, I did the calibration at 4.01 and 6.86. Then I tested some distilled water and the meter read 8.0 at first, after 1 minute it read 6.5 and after about 2 minutes it read 6. I bought another one of those yellow pH pens and after the same calibrations the reading it gave just cracked. Everywhere, everywhere, everywhere. The TDS test pen seems to work, with a bit of variability, although I don't have anything to compare as a benchmark. The temperature readings were stable and seemed correct.