[Why do you need pH and DTS & EC meters] it is a tool to improve your quality of life. these testers can be used to test drinking water, swimming pools, fish tanks, RO systems, or hydroponic water. Any environment that requires testing of watercan use these testers to get accurate data. You have to be safe because water can be life, but can be dangerous. [Test your water with this TDS and EC meter] - Is your water pure and drinkable? With the push of a button, the TDS water quality tester will tell you your overall water purity level, which will be displayed on the screen in ppm. Our pen can quickly displaythe conductivity level of water (Conducts Electricity (EC)) also; it means the dissolved minerals (ions) in water are what conduct the electricity. Finally, you will know the level of pollution and mineralization of water. [Automatic temperature compensation] - There is no need to worry about the temperature of the test liquid affecting the measurement results, as both the pH meter and TDS meter have an automatic temperature compensation function that adjusts to the watertemperature [pH tester] Full measurement range of pH 0 - 14, reliable and quick readings. How to calibrate pH pen - Press CAL key for 3 seconds to enter calibration mode, then press to select 6.86, 4.00, 9.18 corresponding powder to finish calibration, pH pen electrodeis easily affected by the environment, if not used often, calibration before use will get accurate measurement results, regular use will keep the accuracy of measurement [Great for all home and laboratory] TDS & & EC and pH testing applications including drinking water, cooking water, aquariums, swimming pools, hydroponic, etc... Not necessary anymore to compare color strips. It's digital reality.