TDS-3 Digital LCD Tester Tap Water Quality Filter Purity 0-9990 PPM Meter Temp Portable Digital TDS3 TEMP PPM Tester TDS Meter Filter Pen Water Quality Purity Measuring Features: 100% Brand New and high-quality This item can be used in water purifiers and filters, food (vegetable, fruits) & drink quality monitoring, pools, spas, aquariums and hydroponics   Hold function: Saves measurements for convenient reading and recording Auto-function: Turns off meter after 10 minutes of non-use to conserve batteries Dual Range: Measures from 0-999 ppm, with a resolution of 1 ppm. From 1,000 to 9,900 ppm, the resolution is 10 ppm Accuracy +/- 2% Battery: 2 x 1.5V Button Cell Battery Weight: Approx 60g   How to calibrate TDS Meter:  1.In the water, hold the temp key for 3 seconds, release the hand when the screen font flashes. 2.Press temp is "+", hold is "-". 3.Adjust the value. 4.Press the temp key for 3 seconds. Calibration ends when the screen font does not flash. Kindly Note: Do not drop the entire TDS meter in water or dip beyond the maximum immersion level (approximately 2" - refer to manual for further information). This unit is not water-tight and will be damaged if water enters the unit.