Wide usage: TDS Tester can be widely used in water purifiers and filters, food (vegetable, fruit) and beverage quality control, swimming pool and spa, aquarium, hydroponic, etc. Three test modes: The measuring principle of the TDS meter is to measure the conductivity of the water, which indirectly reflects the TDS value. With the hold function you can save, read out and save the measurement results. Three test modes: ON/OFF is the switch button, HOLD is the lock button, and TEMP is the mode button, which can be customized according to personal needs. Easy to handle: The TDS tester can detect some impurities in water, such as soluble salts, ionic organic compounds, heavy metal ions, etc., bringing great convenience to you and your family to get cleaner water. No matter where you are, travel/game/shopping, check the water's TDS value at any time with a measurement accuracy of 2%. Auto-off function: If there is no operation for 5 minutes, the TDS tester will shut down automatically to save power. To prevent the battery from being discharged. Measuring range: 0-9990ppm, resolution is 1ppm. From 1000 to 9990ppm the resolution is 10ppm. A notice:The TDS pen cannot be used to measure high temperature water (e.g. hot water) or water with strong shaking. Notes:1. Due to manual measurement, please allow 1-3 cm error. Make sure you don't mind before you bid.2.Colors may vary due to different monitors, please understand. Thank you for your support :)