Hanna Instruments Portable PH EC TDS Meter HI9813-6 is an economical waterproof portable meter that measures pH, conductivity (EC), total dissolved solids (TDS) and temperature with a single probe. The HI9813-6 features the Hanna Instruments CAL Check that will allow the user to know when the probe needs to be calibrated or replaced. The meter operation is simplified with dedicated buttons for measurement modes to be be displayed on the LCD and knobs for single point calibration of pH and EC. The HI9813-6 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. This range is suitable for agricultural, greenhouse and hydroponic applications. The temperature correction coefficient (β) is fixed at 2%/°C.