Scope of application: pure water production and drinking, electroplating liquid, boiler water, fish tank water and swimming pool water, cleanliness, photographic liquid, wells, deep well water, laboratory, aquaculture, food processing, home, office, teaching, ionization water, cosmetics, city government water supply, travel health care. Instructions : 1. Remove the cap from the pen and turn the switch on. 2. Dip the pen into the test solution but not more than 2cm. 3. Stir the pen in the solution, then stay stable and after 2-6 seconds the TDS value will display on the screen. Press the hold button to save the value and then look at it. 4. After using, dry the head the of the pen and put the cap back on. Please note: The body of the TDS pen should not be exposed to liquids, direct sunlight or high temperature. Avoid dropping it. Specifications : Type: TD Meter-K12 Color: White Measurement Range: 0~999ppm Accuracy: ±2% (F.S) Power: 2 x 1.5V CR1620 button battery Automatic Temperature Compensation: 0~60ºC Operating Temperature: 0 ~50ºC Weight: 55g Size: 154mm x 30mm x 14mm Package contains: 1 x TDS Meter K-12 2x 1.5V CR1620 Button Cells 1 x TDS Meter Carrying Case 1 x TDS Meter User Manual