High Accuracy & Easy to Use: The maximum tolerance is less than +/- 2%, and the operation steps are simple. Wide Use: 0-999 PPM measurement range. Ideal tool for testing drinking water, aquariums, RO/DI systems, hydroponics,pool,etc. Fast Read & Auto-off Function: Use intelligent detection chip, which can be read on the digital screen of Total Dissolved Solids instrument within one second. After 10 minutes of inactivity, the Meter will automatically turn off to conserve battery power.This product is auto-calibrated and is ready to use Do not immerse meter in liquid beyond the maximum immersion level of 4 cm. & Do not store meter in high temperatures or in direct sunlight. The large backlight LCD has been upgraded for easy reading, and has an automatic lock function for ease of use