CALL A.WIHARTA 081294124885 085778084789 087784022201 This indicator continuously monitors the three most crucial nutrient parameters in hydroponic, greenhouse and horticultural applications. At startup, HI 991404-01 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. Please Note: This item cannot work with a digital ballast.