This indicator continuously monitors the three most crucial nutrient parameters in hydroponic, greenhouse and horticultural applications. At startup, HI 991405-01 performs a self-check to assure proper working condition. The stability indicator and HOLD function lets the user know when to take readings and freezes the reading on display for easy and accurate recording. This instrument is supplied with a non-clogging double junction pH electrode as well as a rugged conductivity probe that will withstand even the most aggressive environments. The 12 VDC adapter makes these instruments ideal for all continuous monitoring applications. Order Information: HI 991405-01 ( 115V) and HI 991405-02 ( 230V) is supplied with HI 1293D pH electrode, HI 7630 EC probe ( fixed) , HI 70004 pH 4.01 buffer solution sachet, HI 70007 pH 7.01 buffer solution sachet, HI 70030 1288 mS/ cm calibration solution sachet, 12 VDC adapter and instructions.