Amprobe WT-20 Conductivity/TDS Pen-Type Water Quality Meter Pen-type water-quality meter measures conductivity and total dissolved solids (TDS), and is used to monitor regulatory compliance and to troubleshoot corrosion in building water and wastewater systems Displays conductivity from 0 to 1,999 microsiemens (uS) or 0 to 19.99 milliseimens (mS), with a resolution of 1 uS (0.01 mS) Displays total dissolved solids (TDS) readings from 0 to 1,999 ppm (0 to 19.99 ppt), with a resolution of 1 ppm (0.01 ppt), and an adjustable TDS factor from 0.4 to 1.0 Two-point calibration has a range of + or - 30 percent of the factory default parameter Complies with Ingress Protection (IP)-65 rating for water- and dustproof housing