TDS meter is a water quality analysis device used to indicate the total dissolved solids in a solution (usually water). Since dissolved ionized solids (such as salts and minerals) increase the conductivity of a solution, a TDS meter can also measure the conductivity of a solution and estimate the TDS from that reading. TDS meters typically quantify this conductivity in microsiemens or ppm. There is tds meter with data logging function and tds sensor for ro system.