It is a cheap and convenient digital tool that can instantly check your overall water quality. TDS means Total Dissolved Solids, which is any salt, metal or mineral in the water. With the push of a button, TDS can tell you your overall water purity, and it will be displayed on the screen in ppm (parts per million). The lower the TDS content, the purer the water, and the pure water is 0 ppm. TDS is very suitable for checking the quality of tap water or knowing when to replace the filter. (The meter does not test for biological contaminants.) TDS is an excellent tool for drinking water, water filtration and purification, silver, hydroponics (testing nutrients), aquariums, /DI systems, swimming pools and spas, commercial and industrial applications, etc. TDS is a rugged and durable model that includes a protective carrying case. This is a globally popular handheld TDS meter for industry . is Perfect for commercial use It includes a suitcase with belt clip fixing function: due to its advanced microprocessor technology and a built-in digital thermometer, measurement data can be stored efficiently and accurately for convenient reading Take and record; display: large and easy to read LCD screen. digital TDS water meters are Perfect for testing applications such as hydroponics and gardening, swimming pools and spas, aquariums and reef tanks, water ionizers, and water filters. TDS water meters are Perfect for testing applications, including Perfect drinking water, water purifiers, carbon filters, , hard water, ordinary tap water, refrigerator water purifiers, water purifiers, hydraulic filters, reverse osmosis, reverse osmosis filters. Measuring range: 0-9990 ppm, 1 ppm resolution, + /-2% reading accuracy. Power supply: 2 x 1.5 V (LR44 button battery) (not included) colour: black Material: plastic Size: 155mm Package Contents: 1 x TDS Pen Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.