【Note:】 Our 5-in-1 PH TDS meter has been calibrated at the factory, you can use it directly. And after a long time of use, if the error of the measured value is large, it can be calibrated with a calibration solution as needed. 【What is a 5 in 1 pH meter】 Tests alkalinity, acidity in water, tds: Total dissolved solids, allows you to test the impurities, EC: Electrical conductivity, can be used to measure soluble ion concentrations in liquid fertilizer or culture, salt: tests salinity and temperature. 【Measuring range】 PH 0.00-14.00 (accuracy 0.01ph), TDS 0-10000ppm, EC 0-10000us/cm and temperature 0-60℃. Retro Illuminated】 This pH meter is designed with a bright green backlit LCD screen, which displays the information in an intuitive way. You can always read digitally even in a low visibility situation. 【Wide Application】This 5-in-1 multi-functional tds tester is ideal for home and laboratory pH testing applications, which can be used to test the quality of drinking water, swimming pools, aquariums and domestic plantings.