This Digital LCD Pen Stick TDS Meter is 100% brand new and high quality. Press the ON/OFF button when you want to turn on/off the tester. And the hold button is aimed at saving measurements for convenient reading and recording. But please remember to press the hold button when you get the tester out of water, and then its hold funtion works. Features: Measurement range of 0-9990ppm and /- 2% highly accurate and quick readingsAuto-off function: the meter shuts off automatically after 10 minutes of non-use to conserve batteries. Display: large and easy-to-read LCD screenMeasurement Range: 0-9990 ppm. From 0-999 ppm, the resolution is in increments of 1ppm. From 1000 to 9990 ppm, the resolution is in increments of 10ppmLightweight, handheld design for portability and convenience; /- 2% Readout AccuracyPocket-size unit is also ideal for home or laboratory hydro-electrical conductivity testing. Ideal for water TDS testing like aquariums, swimming pools, water filters, and more Specifications: Range:0 - 9999mg/LResolution:1 mg/LAccuracy: - 2% F. SWorking temperature:0 - 50CSize: 150mm27mm20mmPower supply:2 x 3V CR2032 batteries(not included) Weight: 46g