A TDS meter measures the concentration of dissolved inorganic and organic substances in water, typically displayed in parts per million (ppm). It works by measuring the electrical conductivity of the water; the more dissolved solids present, the higher the conductivity. This tool helps determine if water is suitable for specific uses, such as drinking, cleaning, or hydroponics. The "hold" function, indicated on the case, allows the user to freeze the reading on the display for easier viewing. With instructions for use included.
eBay