Keyestudio TDS sensor kit is compatible with Arduino controllers, plug and play, easy to use. It can be applied to measure TDS value of the water, to reflect the cleanliness of the water. TDS (Total Dissolved Solids) indicates that how many milligrams of soluble solids dissolved in one liter of water. In general, the higher the TDS value, the more soluble solids dissolved in water, and the less clean the water is. Therefore, the TDS value can be used as one of the references for reflecting the cleanliness of water. Measuring the TDS value in the water is to measure the total amount of various organic or inorganic substances dissolved in water, in the unit of ppm or milligrams per liter (mg/l). Its Electrode can measure conductive materials, such as suspended solids, heavy metals and conductive ions in water. The module comes with four 3.2mm fixed holes, easy to mount on any other devices.