Review on Poit Digital Meter Tester Resolution by Wagner Witlin

I would say 4 1/2 stars, rounded up to five. After experimenting a bit, I decided to test the calibration with the pH 6.86 bag that came with the instrument. I pressed the calibration button. I then bought two bottles of pH calibrated solution at 4:00 am and 7:00 am. The readings I got from the meter were erroneous, 4.3 and 6.7 respectively. I figured I messed up the calibration by not using distilled water, assuming the buffer pack would take care of everything. So I recalibrated as follows: - a bag of pH 6.86 powder in distilled water - a pH 4.00 solution (the meter is smart enough to figure out what target to calibrate to). Thereafter, the readings of the solution 4.00 and 7.00 were within 0.05. , although it takes a few seconds to achieve the last ounce of precision. So I'm happy with the meter, although I wonder why I got a compressed range first before doing a more thorough 2-point calibration that covers the range I'm interested in. (I didn't do a high pH calibration as my solution is in the 6-6.5 range).