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Our handheld TDS testers, in-line monitors, controllers and demonstration devices for reverse osmosis (RO) water filters and water purification systems are superior in construction and performance, yet made available at a very economic cost. HM Digital, Inc. Is the only manufacturer of economical in-line dual TDS meters that measure total dissolved solids (TDS) levels of feed and product water lines simultaneously, an effective way to compare rejection rates and gauge reverse osmosis membrane, water filter and water purification performance.

Established in 1989, HM Digital, Inc. Known as Heemang Manufacturing) is an original equipment manufacturer (OEM) that has been recognized worldwide for providing the best values in water testing instrumentation, especially the increasingly popular TDS meter. Our ISO-9001-certified factory in Seoul, Korea designs and produces high quality water testing and monitoring equipment for all types of water treatment and purification systems, including reverse osmosis (RO) that are sold in over 50 countries throughout the world. We also offer OEM services for customized products and private labeling