[ 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. Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! [ 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., Weight: 0.13007273458 Pounds, Manufacturer: Ehwisbe