HM Digital COM100 Waterproof EC/TDS And Temperature Combo Meter plastic Imported Measures electrical conductivity (EC), total dissolved solids (TDS), and temperature Four scales: S, mS, ppm, ppt (mS and ppt are new) Three different nonlinear ECtoTDS conversion factors (KCl, 442TM, NaCl). Waterproof housing (IP67 rating) Measurement Range: 09990 S; 08560 ppm; 09.99 mS; 08.56 ppt