This item is labeled '3-in-1 Precision Hand Water Quality Check Pen' but does not measure PH at all. It's just a TDS meter. Also, the "English" manual has very bad grammar.
TDS water quality tester - TDS water hardness meter (portable digital salt meter for water analysis)
9 Review
Digital PH Meter Tester - Tiaoyeer Water Quality Tester With ATC, 0.01PH High Accuracy, 0.00-14.00 Measurement Range, 0.01 Resolution For Drinking Water, Aquarium, Swimming Pools, Hydroponic
8 Review
Portable digital multimeter with sound continuity and thermocouple (electric tester) LTX DT-838
7 Review
π― Honey Refractometer with Automatic Temperature Compensation (ATC) - Tiaoyeer Moisture, Brix, and Baume Refractometer for Honey, 58-90% Brix Scale Range - Honey Moisture Tester
31 Review