Water Tester, Zsunda Professional Water Quality Tester with TDS, EC and Temperature Meter 3- in-1, 0-9990ppm, Accurate Water Meter for Drinking Water, Aquariums and More PROFESSIONAL 3-in-1 WATER QUALITY TESTERAccurate TDS meter, EC meter, and Temperature meter. Ideal water test kit to test drinking water purity, water hardness and its nutrient levels. NATIONAL STANDARDS: National standards adopted TDS figure 40 as the guideline. The backlight turns green when the figure is below 40, indicating acceptable drinking water. While the TDS meter turns to red in the backlight when the figure is over 40, noted as non-drinkable water. (Note: Testing water @ 77 provides the best accuracy.) UPGREDE LCD SCREEN BACKLIGHT: The TDS meter device is designed with a low-power backlight, so it can be used in low light conditions. The TDS Tester will shut itself down if you dont use it for 2 minutes or more, saving battery life. ACCURATE READERS: To achieve high accuracy, the meter is equipped with sensitive electrode sensor and premium titanium alloy probe, you can get an accurate readings quickly. Zsunda professional TDS pen provides a more accurate ppm range from 0 to 9999. The higher of the digits, the more accurate figure is. ZSUNDA WARRANTY: Customer satisfaction is our primary goal. You can get the water test, user manual, our fan-favorite 18-month warranty and friendly customer service from Zsunda.