Review on FOMOOUR pH Meter - High Accuracy Water Quality Tester - 0.01 pH Measurement Range - Ideal for Water, Brewing, Food, Soil, Sauce, and Laboratory Testing - Includes TDS Meter and pH Pen by Michelle Miller

Not sure if I have a bad gauge but it didn't work for me. I tried it right out of the box. It does not work. The reading just kept moving, it couldn't stand the pH. Even after holding it in water for 2 minutes. So I used the bundled packages to calibrate it. The first 2 packages were available. And he kept that number. With the third package I had to try several times to get this number. So I'm back to test the water and hydroponic mix. The counter just doesn't keep the number, it just keeps moving. This starts around 7.0 and will continue to fall and fall. I doubt my filtered water is less than 4.0. I tested it with drops and it's 7.0. I have read the instructions and realized that I may need to leave the meter in the water for a few hours to rehydrate the sensor. Still does not work. So many reviews for a 4 star product. Either I'm doing something wrong or I have a bad meter. I'm looking for a new counter. A bit expensive. Hope something works.