Apera Instruments TDS20 Pocket TDS Tester Kit is built for professional TDS measurement of general water solutions, including tap water, agriculture, aquaculture, pools& spas, education, environmental monitoring, etc. Range: 0-100. 0 ppm, 0-1000 ppm, 0-10. 0 ppt (10, 000 ppm), Accuracy: 1% F. S. 1-2 points auto. calibration, 0 to 50˚C auto. temp. compensation. The BPB (Brush-Resistant Platinum Black) sensor adopts Apera's special processing technology, which minimizes electrode polarization, expands measuring range, and increases firmness of the electrode, hence ensuring a much higher accuracy and consistency in a wide-range TDS measurement than traditional stainless steel electrodes, and is easy to clean. The large LCD screen has ppm/temp. value dual display and indications of completed calibrations and stable readings. Practical functions to make your TDS testing easier and more reliable: 2-point auto calibration, 0 to 50˚C auto. temp. compensation. Customizable TDS factor from 0. 4 to 1. 0. Self-diagnosis with out-of-range and low battery warning. Complete kit: TDS20 meter, 2 bottles of calibration solutions, AAA batteries, and a lanyard all in a portable carrying case. IP67 water-resistant. Up to 1000 hours of use powered by 4 AAA batteries. Low power alarm and auto. power off in 8 min if no operation. The product is CE and RoHS certified, and is manufactured under an ISO 9001: 2015 certified quality system.