Features: TDS means Tatal dissolved solids, which stands for impurities dissolved in water. the greater the TDS value, the higher the impurity content in the water, and vice versa, the lower the impurity content. The general conversion ratio of water hardness GH to TDS value: 0-89ppm(s), strong soft water 0-4dh; 90-159ppm, soft water 5-8dh; 160-229ppm 9-12dh, medium hard water; 230-339ppm, medium hardness 13-18dh; 340-534ppm, water 19-30dh; over 535ppm. Hard water over 30dh. Measurement range: 0-9999ppm Error range: 2% Temperature range: 0-80C Battery: 2 x 1.5v (button cell CR2032) Product size; 15.5*3.1*2.3 (cm) Package includes: 1 x TDS test penNote: 1. Please allow a little error due to manual measurement. 2. Please understand that the colour may vary due to different monitors. Note: Hello, please note your delivery address when purchasing the product. If your receiving information (e.g. name, street, door number, door number/mail without name, etc.) is incorrect, the order will not be delivered properly.