Had the same problem with many others. It's a bit off, even if it's factory calibrated they did it lol. That's why I gave it a 4. But where to speak of 0.01, so no big deal. Overall for the price. and the money I had then. I received them, they work, I still use them today. I wish they were waterproof but that's why they make them. What I will get from vivosun. Because they are good pens. You just have to improve that accuracy and it will be solid.
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
80 Pieces Water Test Litmus Strips Litmus ph Paper Soil Acidity Meter Liquid pH Tester 1-14
10 Review
Portable digital multimeter with sound continuity and thermocouple (electric tester) LTX DT-838
7 Review
π¬οΈ BIAOLING Accurate Formaldehyde Multifunctional Recording: Say Goodbye to Indoor Air Pollutants!
3 Review
π Unveiling Fluke 107: A Cutting-Edge Handheld Multimeter for Accurate Current Measurements
3 Review
Accurate Formaldehyde Multifunctional Detector Recording
3 Review
Airthings 2960 View Plus Humidity Sensor
3 Review