FAST AND ACCURATE READINGS -- Just turn it on, dip in liquid and read display, no need to work with color charts or test strips; Large digital display makes it easy to read. AUTOMATIC CALIBRATION-- Water quality meter pen no need any adjustment screwdrivers, just finish the calibration with Auto calibration button. PORTABLE DESIGN-- Handheld TDS tester pen style and makes it conveniently fits in your pocket or bag and goes anywhere. WIDE APPLICATION-- Ideal for home and laboratory Water Quality Meter applications, including drinking water, swimming pools, Hot Tub ,aquariums, hydroponics,Water filter pitcher etc.