TDS-3: Making Waves

May 31, 2019

About the author:

Jessica Moorman is associate editor for Water Quality Products. She can be reached at 847.391.1012, or by e-mail at [email protected].

It is hard to imagine that an instrument weighing only 2 oz could make ripples in the water industry. The pocket-sized TDS-3 meter from HM Digital, however, is doing just that. After less than a decade on the U.S. market, this meter has become one of the most popular handheld TDS meters for water professionals.

HM Digital attributes the success of this meter to its high quality, features, and the company’s commitment to customer service.

Water Quality Products asked several product distributors to offer their feedback on the product, and they agree.

“It is the most requested meter on the market,” said Sean Caughron, water filtration sales manager for Chester Paul Co. “The price is right, and you can’t beat the performance. Usually these two things never line up; the TDS-3 is an exception to the rule.”

Humble Beginnings

Established in South Korea, HM Digital (formerly Heemang Electronics) developed the TDS-3 in 1995. After strong initial interest in the TDS-3 in Korea and Asia, HM Digital introduced the TDS-3 to the U.S. market in 1997, and opened its first U.S. office in 2000. The company started small with direct telephone sales, and after expanding its office and marketing in 2002, soon switched to a distributor network approach.

While many users were at first hesitant or even reluctant to switch from established brands, those who took the chance never looked back. With applications for everything from water purification and wastewater regulation to aquaculture and hydroponics, the TDS-3 is an ideal instrument for measuring TDS.

“The TDS-3 is one of our most popular instruments, if not the most popular, said Steve Norvell, president of “Sales have increased steadily every month. So far, in the first half of 2006, we’ve already doubled our sales of this meter from the first year we carried it.”


The high quality of the TDS-3 is its main selling point. With a long lifespan, many features, little to no maintenance and a three-year warranty, the meter has established its top place in the market.

“Customers love the reliability and accuracy of the meter,” Norvell said. “It is extremely durable and comes in a vinyl case, so they don’t have to worry about the meter getting banged up or broken. It is important to the customer to make sure that the meter can take a beating, but still perform optimally.”


The TDS-3 meter comes with various features, making it convenient, reliable and suitable for a wide range of applications. According to HM Digital, some of these features include:

Wide range. The TDS-3 is an auto-ranging meter covering 0 to 9,990 ppm. This feature allows the TDS-3 to be used for various applications.

Resolution. The resolution of the meter is 1 ppm for 0 to 999 ppm and 10 ppm for 1,000 to 9,990 ppm.

Display. The TDS-3 includes a large, easy-to-read LCD display.

Hold button. A conveniently located hold button allows users to view and display the reading out of the water with the touch of a button.

Battery life. The batteries last for approximately 1,000 hours. The meter takes two small button-cell batteries, which can be found in most electronics stores, supermarkets or drug stores.

Auto-off function. To help conserve battery life, the meter will shut itself off when not used after 10 minutes.

Accuracy. The accuracy of the meter is ±2%, which is suitable for almost all applications.

Calibration. The meter comes factory-calibrated at 342 ppm NaCl, but can be easily recalibrated with a small screwdriver.

Customer Service

Besides offering a quality product, HM Digital takes prides in its commitment to customer service. Whether a customer needs to place an order, contact the company for warranty service or just has a question, the customer will almost always reach a person on the phone. In addition, messages and e-mails are always returned within 24 hours with complete, helpful information, according to HM Digital.

“In all the years I’ve been doing business with them, I haven’t had a single customer service issue,” Norvell said. “Somebody always answers the phone, and they answer e-mails within a day or less and ship the day I order.”

According to Scotty Murch, vice president of international sales for Watts/Flowmatic, “HM Digital is a very good supplier as they have very quick turnaround for orders, cost is competitive in the industry, they have a broad range of products, and most of all, they support the master distributors that commit to their product line by sending us leads and training our sales staff on their products to help us generate more sales as well. With all of these great features, Watts flowmatic looks forward to its continued success with HM Digital for many years to come.”

About the Author

Jessica Moorman

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