Review on PH Meter, TDS PPM Meter, Soil PH Tester - Digital Kit (3 Pack): Accurate Testing for Optimal Growing Conditions by Dawn Kraft

My first purchase, a water pH tester, was very inaccurate. It showed a reading of 4-5 ph for distilled water. I then attempted to calibrate it using the supplied buffer packs and instructions. Still didn't work - it read pH 6.86 water as 4.4, didn't even register pH 4.0 water and showed pH 9.18 water as around 7. I figured it was a mistake and arranged for a replacement through Revain. I got a new one today and tried again. The same thing. This pH reader correctly reads slightly low readings and will not recalibrate to correct values. I think I'll be returning the second set as well. What a waste of shipping and packaging.