Remove the pen cover and turn on the ON switch; Put the pen into the test solution, the height of the solution should not exceed 2cm; Swirl the pen in the solution, once the reading is stable (2-6 seconds), the TDS value will show on the screen, then press the HOLD button to lock the value. After use, wipe off the water on the tip of the pen, rinse with pure water, and close the pen cap. < p> Precautions for use: avoid immersing the TDS pen in water, avoid direct sunlight, keep away from high temperatures, avoid strong shocks and drops. Product use range: Detect whether the quality of tap water, purified water and mineral water meets national drinking water standards: tap water is less than 300 ppm, pure water is less than 50 ppm (national standard) and mineral water is between 100 and 200 ppm . Specifications of the test pen are as follows: Wide measuring range can measure 1-9999PPM. Applicable temperature range 0-50 degrees to operate, -30 degrees can be stored. LCD display window large screen LCD display Waterproof design, easy to watch, durable Long battery life Use 2 x CR1620 3V batteries, they can be used for more than 3 years and the auto-off feature will save battery power if not used for 10 minutes. (battery not included) Reasonable design the pen tip electrode can be directly inserted into the measured aqueous solution for measurement, and the pen cover can also be used as a container for the measured aqueous solution, which is extremely convenient. Package contents: 1 TDS pen. Note: The data is all manual measurement, please allow 1 - 3cm error, due to the difference in light and display, there will be a certain difference in color, depending on the physical object received Delivery Quantity: (according to the main image)