The Hanna Instruments HI 9813-6N Hydroponics pH/EC/TDS/C meter is a versatile, water resistant, multiparameter portable instrument specifically designed for agricultural applications such as hydroponics, greenhouses, farming and nurseries. + The Hanna Instruments HI 9813-6N features an large LCD that clearly displays the parameter being measured as well as calibration instructions. Calibration is fast and easy with knobs located on the front panel of the instrument. The Hanna Instruments HI 98136 includes all the features of the Hanna Instruments HI 9813-6N while incorporating our exclusive CAL CHECK feature. + CAL CHECK allows the user to easily check the pH probe calibration status at any time. The Hanna Instruments HI 9813-6N utilizes the HI 1285 series pH/EC/TDS/temperature probe. This probe features a fiber junction and gel electrolyte making it ideal for fertilizer solutions.