Function: Tests the quality of various waters and ensures you enjoy the best water quality and temperature (it cannot test pH or a specific value of a substance dissolved in the water). Lock function: Saves measurements for easy reading and recording. Auto function: Turns the meter off after 10 minutes of non-use to save battery life. Dual range: Measures from 0 to 999 ppm with a resolution of 1 ppm. From 1000 to 9900 ppm, the resolution is 10 ppm. Suitable: This product can be used in water purifiers and filters, for monitoring the quality of food (vegetables, fruit) and beverages, in swimming pools, spas, aquariums, and hydroponics.