Established in 1987, HM Digital, Inc. (formerly known as Heemang Electronics) 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 products are co-designed between our Los Angeles office and our ISO-9001-certified factory in Seoul, Korea, producing 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.

In 2000, the US office was established in Los Angeles, CA to provide marketing, customer service and distribution for the Americas, Europe, Africa, the Middle East, Australia and South Asia. We strive to always provide the best values as well as the utmost care in promptly serving our distributors and customers.

Our handheld and portable TDS, EC, pH and ORP testers, in-line monitors, controllers and accessories for reverse osmosis (RO) water filters, water purification systems, hydroponics, aquariums, pools and many other applications 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 monitors 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.

With HM Digital water testing instruments, you'll know if your water is pure.

What is TDS?