Aurosports 3-in-1 Water Quality Tester Professional TDS, EC and Temperature Meter With Protective Leather Case Backlight LCD screen, Green backlight means 40ppm below, Red backlight means more than 40ppm Digital aid combo test meter With 3 buttons, shift TDS to EC, with ATC function Hold function, easy to read or record, press "ON/OFF/HOLD" button then remove from test solution 1 minute Auto Shut Off feature, so battery won't run down and protect your meter Measurement range of 0-4990 ppm,0-9990 s/cm, 0.0 - 99.0C, 32.0-210.4F, 2% accuracy