Red backlight = non-drinkable warning (>50 ppm), green backlight = directly drinkable (<50 ppm). 【Multipurpose Tds Tester】 Test the purity of drinking water to ensure it's safe and healthy, monitor if Reverse Osmosis (RO)/Deionization(DI) System works properly, whether filter need replaced, maintenance aquarium, hydroponics(test nutrients), well, pool, hot tub, spa and testing tap water, bottle water etc.
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