BeGrit Handheld TDS Meter with Digital Thermometer, 0-9990 ppm Measurement Range, 1 ppm Resolution, 2% Readout Accuracy The BeGrit TDS tester is ideal for all water purification applications, wastewater regulation, aquaculture, hydroponics, and colloidal silver Hold Function: Saves measurement for convenient reading and recording. Display:easy-to-read LCD screen Auto-off function: the meter shuts off automatically after 5 minutes of non-use to conserve batteries Measurement Range: 0-9990 ppm. Dual Range:From 0-999 ppm, the resolution is in increments of 1ppm. From 1000 to 9990 ppm, the resolution is in increments of 10ppm, indicated by a blinking 'x10' image Use The BeGrit TDS tester: Check the performance of your water filter. Check for hardness. Make sure you always drink pure water