The Hi9813-6 is an economical, water resistant, portable meter that measures pH, conductivity (EC), total dissolved solids (TDS) and temperature with a single probe. The meter operation is simplified with dedicated buttons for measurement modes to be displayed on the LCD and knobs for single point calibration of pH and EC/TDS. The Hi9813-5 has a variable EC to TDS conversion factor that automatically changes from 0.56 to 0.78 ppm = 1 µS/cm based on the actual EC reading