[TEST YOUR WATER PURITY] With this lightweight conductivity meters pen can test the water purity, Just stick it in about 1 inch deep of water, then TDS water tester can tell you your overall water purity level, which will be displayed on the screen in ppm (parts per million).[MULTIFUNCTIONAL AND UPGRADED] Professional TDS, EC and Temperature Pen 3 in 1. Upgraded with big backlit LCD for easier reading, and auto-lock function for easier use.[ EASY TO USE AND HANDY] Just stick the TDS meter tester into the water of 1 inch deep, then stabilized readings will be auto-locked on LCD screen in seconds, TDS tester shuts off automatically after 3 minutes of non-use to conserve batteries. Features a hold function that saves measurements for convenient reading and recording.[What is TDS] The TDS meter is a great water quality tester tool for water testing kits for drinking water, drinking water, water filtration and purification systems such as RO or DI systems, aquariums, hydroponics (test nutrients), pools and spas, commercial and industrial applications and more. Suitable for checking your tap water quality and knowing when to change a filter.[Many uses] In addition to the known reliable mineral water, other pure water needs to measure the purity of the water, which can protect the health of children, the elderly and pregnant women.