Dear customer, Thank you for choosing our products. If there is any problem with our products, please contact us through the order information. We will be happy to serve you and solve it for you as soon as possible within 12 hours, thank you! Accurate and ReliableTDS meter measuring principle is to measure the electrical conductivity of water and indirectly reflects the TDS value. Test Your WaterTest the impurities in water such as some elements of soluble salts, ionic organic compound, heavy metal ion, etc, offering much convenience for you and your families to get a more clean water. Hold FunctionIt supports hold function that can save measurement results for easy reading and record. Simple and InstantJust turn TDS meter on and stir water gently, then stabilized readings will be auto-locked on LCD in seconds, And shuts off automatically after 5 minutes of non-use to conserve batteries. Multifunctional TDS TesterThe TDS meter can be widely used for aquarium, beverages, quality control, fish hatcheries, food processing, laboratory, schools, colleges, swimming pools, etc.