Established in 1987 HM Digital, Inc. continues to be a worldwide leader in EC, TDS, pH and ORP water testing instruments offering handheld meters, in-line monitors, controllers and accessories serving the needs of a wide variety of markets. (These include reverse osmosis (RO) water filters, water purification systems, hydroponics, aquariums, pool and spa, window cleaning, cooling towers and many other applications). By offering superior products at an affordable price, HM Digital has positioned itself to be the ideal choice for anyone looking for reliable water testing products.