The PinPoint Conductivity Monitor is an instrument for the measurement of hardness in freshwater. The conversions are 33 µS=17.9 ppm=1dH. Good quality reverse osmosis water measures 515 µS, while de-ionized water measures 01 µS. The Conductivity Monitor is automatically temperature-compensated and has two ranges, making it useful for different applications. The freshwater hobbyist will appreciate the instant readings for precise hardness. The saltwater hobbyist will use the PinPoint Conductivity Monitor to assess the purity of deionized and reverse osmosis water. Given proper care, the PinPoint Conductivity Monitor should last a lifetime. PinPoint Conductivity Probe is permanent and may never require replacement. Powered by a standard 9-volt battery (not included). AC Adapter Kit available. User Guide (AmericanMarineUSA.com Web site in new window)