Apera Instruments TDS20 Value Waterproof TDS Pocket Tester, Accuracy: &plusmn;1% F.S, 0.5C, Complete Kit Easy Auto Calibration with buffer recognition; Auto Temp. Compensation (ATC) ensures accuracy in variant temperatures (0-50.0C); Accuracy: 1% F.S, 0.5C; Range: 0-100.0 ppm, 0-1000 ppm, 0-10.0 ppt EASY Auto Calibration with auto buffer recognition; Auto Temp. Compensation (ATC) ensures accuracy in variant temperatures (0-50.0C) LARGE CLEAR LCD with DUAL Display of temp./ppt, and REMINDERS of completed calibrations and stable readings COMPLETE KIT with READY-TO-USE calibration solutions, batteries, and a lanyard in a portable carrying case 1000 hours' continuous operation time powered by AAA batteries