Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! [ LCD BACKLIGHT ] : Our TDS water meter is equipped with low-power backlight technology, which makes it easy to test water at night or in dark places. It can also be used to distinguish drinking water from non-potable water. The red backlight (ppm 40) reminds users that the current water quality is not ideal, indicating that it is not potable. [ Test Function]: With the advanced (TDS, EC, Temperature) conductive pen, the tester can not only detect TDS, but also EC and temperature in the water. The ppm meter ranges from 0-9990 ppm, and the temperature also supports two reading modes: Celsius and Fahrenheit. Simple and easy to operate: Simply turn on the TDS meter, gently stir the water, and within seconds the LCD display automatically lock, and the TDS meter automatically turn off after 2 minutes of inactivity to conserve batteries. Instructions for use: 1. Remove the pen cover and the ON button to turn on the tester. 2. Place the pen in the solution to be tested, the height of the solution should not exceed 4 centimeters (from of the pen). 3. Stir gently several times in the solution to be tested and wait for the reading to stabilize within a few seconds. 4. After use, dry the water on the tester with a cloth and wipe dry with the cap of the pen. Widely used in all water quality testing, water purification applications, aquaculture, hydroponics, swimming pools and silver, water treatment and so on. You can test tap water, filtered water, distilled water, bottled water, well water, cold water, etc. It is a necessary and convenient tool for . The actual product may have slight color differences or differences, which does not affect use. Colour:black+white Material:plastic Package Contents: 1 x Tds Meter Only the above package content, other