APPLICATIONS FOR ALL: Water purification, Wastewater plant, Aquaculture, Hydroponics, Colloidal silver, scientific labs, Pools/Spas, Ecology, Food Processing, Physics/Chem labs, Cosmetics, Home/Office, RVs. Product Features 1. Digital display: accurate to 4 digits. Temperature compensation accurate to 0.1 2. Backlight function: green backlight while TDS value ?40, red backlight while TDS value>40. 3. Auto-lock: TDS value stabilizes 4 seconds, instrument automatically lock readings. 4. One Touch function: