The History of YSI on the 70th Anniversary

The History of YSI

An Entrepreneurial Spirit

(Updated August 2021)

YSI was founded on the spirit of innovation. The burning desire to solve a problem, develop a solution, and change the world is woven into the fabric of YSI and our team.

It all started in Yellow Springs, Ohio in 1948. In the beginning, two engineers, Hardy Trolander and John Benedict, embraced their entrepreneurial side, setting out to solve the problems of the day through the application of good science. They were joined by chemist David Jones.


Hardy Trolander and Dave Case in 1954 doing what they loved - solving a problem. 

With an investment of $100 each, the three friends began the Yellow Springs Instrument Company (YSI). Shortly after the founders incorporated the company, Hardy was appointed the first President. They were joined by David Case, another Antioch College alumnus (and tinkerer).

Together they collaborated with the Fels Research Institute at Antioch University on medical research. But, like many struggling start-ups, the team was willing to take on just about any project. Eventually, they bid on a job at the Wright-Patterson Air Force Base (formerly Wright Field) with the help of Fred Hooven, who became the fifth stockholder. Hooven had gained a reputation for his significant contributions to the Army Air Corps, among them being the principal inventor of the automatic radio compass, which is still in use today.


YSI manufacturing in 1951.

Some of YSI’s first instruments included a camera timer, dielectric constant meter, telethermometer, and even an integrated radio for Huffy bikes.

Believe it or not, the Huffy radio bike was not the contract that put Yellow Springs Instrument Company on the map. Our founders’ big break turned out to be a contract for high accuracy camera timers.

Trolander said of the early days, “There is an awful lot to be said for pigheadedness and for being too dumb to know what we should be doing. We weren’t so driven that we had to get a big return.”


The YSI radio on a Huffy bicycle in the mid-50's.

In the mid-1950’s joint research at the Fels Institute was progressing and led to the development of YSI thermometers to measure core body temperature in sedated patients. This new instrument was developed for the healthcare industry, but the temperature readings were so stable and reproducible, NASA pulled them off the shelf for use in outer space. And, in fact, in late 1955 the company’s first interchangeable thermistor temperature probes were used extensively in the U.S. space program.

Getting Started In Medicine

The history of YSI would be incomplete without the mention of Dr. Leland Clark, to whom not only YSI, but the world, owe a debt of gratitude. Dr. Clark was a researcher at Fels with whom Hardy Trolander and the others worked closely. He is best known for having developed the aptly-named Clark polarographic oxygen electrode that allows dissolved oxygen measurement in liquids (Learn more about dissolved oxygen, download The Dissolved Oxygen Handbook). Applications of this technology were endless and included environmental, biomedical and industrial sensing.

Early on, Dr. Leland Clark and Hardy Trolander wrote an article that led to several developments and new instrumentation possibilities. This marked the beginning of several decades of collaboration on a wide range of medical devices.


Dr. Leland Clark inspecting membranes and sensors.

Dr. Clark’s heart-lung machine paved the way for open heart surgery. He developed an electrode that could measure the oxygen in the blood and found a particular membrane that would allow these measurements to be consistent and reliable. YSI produced these electrodes in the first commercialized design.

This development led YSI employees (and the public) to realize the potential for dissolved oxygen measurement in other applications like environmental waters. Soon thereafter, the area’s local utility, Dayton Power & Light Company, approached YSI with concerns about thermal pollution discharge within the nearby Great Miami River. The team didn’t know it at the time, but these initial conversations were YSI’s first step into environmental monitoring.

Who’s Minding the Planet?

YSI was in the business of minding the planet before the word recycle was in the dictionary and before Earth Day and global climate change were common themes.

Who's Minding the Planet is more than a tagline, it's a way of doing business and working with WMTP_Only__Horizontal.jpgscientists, engineers, and more who live it every day. Share your Who's Minding the Planet stories and pictures on social channels with the hashtag #WMTP.

This environmentalist culture led to the development of a long line of highly precise water quality instrumentation that continues to this day. In 1963, YSI introduced the first commercial dissolved oxygen meter for field and laboratory. Not long after, the company produced the first biological oxygen monitor and quickly became recognized worldwide as the leader in dissolved oxygen measurement and DO technology.


YSI commercialized the first dissolved oxygen meters utilizing the Clark polarographic membrane technology based on Dr. Leland Clark's discovery allowing us to become the leaders in DO measurement.

That recognition didn’t come easily. YSI didn’t become a household name in the environmental space overnight. Ray Schiff, who established the early distribution network for YSI instruments reminisced, “…We had to go overseas and set up similar supply houses and distribution to build our business. So, I bet $1,000 I could do it and set it up... I got a list of various countries and I was able to set up distributorship in Europe by pounding the pavement.” Ray had no intentions of losing his bet.

His work helped to equip environmental scientists around the globe with the most accurate sensors for their work, and many of the business partnerships he built and nurtured are still in effect today.

The Next Generation

During the 80’s, Hardy Trolander stepped aside and opened the doors for his successor, Malte von Matthiessen.

“When I came here, I discovered there was a high level of appreciation for what had happened before my arrival.” Von Matthiessen said, “What I did was simply build on Hardy’s successes.” At the time, YSI had three core businesses including the temperature division, life sciences division, and environmental division.

After several years with Malte at the helm, YSI began to sharpen its focus on product development and replaced the traditional hierarchical managerial structure with cross-functional and self-directed teams. He also established an Employee Stock Ownership Plan (ESOP) where all employees became owners of the company. His innovative leadership style helped define the organization for decades to come.


The next generation of scientific discovery and curiosity is always important to YSI.

During Malte’s tenure at the company, YSI: 

  • Implemented a set of core company values to drive the business with a focus on ecological sustainability, employee ownership, community, and innovation
  • Established the YSI Foundation to support charitable and environmental causes
  • Adopted the ‘Who’s  Minding the Planet?’ tagline to build the brand through the commitment to environmental stewardship
  • Acquired Endeco (now YSI Systems), allowing the company to enter the environmental monitoring markets for the ocean and coastal applications
  • Opened the new state-of-the-art R&D facility along with offices in Japan, Hong Kong, and China
  • Introduced the first ‘6-Series’ sonde, marking the beginning of a highly successful line of multiparameter, continuous water quality monitoring instruments
  • Introduced a multiparameter platform automated biochemistry analyzer
  • Introduced multiparameter recirculating system monitor for aquaculture
  • Acquired SonTek, adding water velocity and flow measurement capabilities to our sensing portfolio for water quality and quantity

Malta inspired a company culture of putting our customers first. Our employees bought into the concept – both literally and figuratively – as part owners of YSI. Over time, this culture manifested into a mindset of ‘how do we help solve customer’s biggest problems’.

As Ian Thompson, now Xylem Analytics Senior Sales Director, stated years ago, “A lot of our products are designed by customers. They tell us what they need and we go to the drawing board and find them a solution. By having customers design products, we can rest assured that our products are being used for good applications.”


We know that many of our customers are doing work that can change the world and, in fact, has.

A Focus On the Environment

After 17 years of dedication to YSI, Malte von Matthiessen retired as CEO, leaving the organization in the capable hands of Rick Omlor in 2002. It wasn’t long before Rick and his leadership team made the strategic decision to focus the business in a select few areas rather than following the company’s 60-year history of ever broadened markets and sensor development. This strategy, focused mainly on the water quality and water velocity applications in the natural resource market. It also led to many of the innovative products that YSI is best known for today in the environmental space.


YSI made the decision to focus the majority of our efforts on the environmental side of our business, specifically, water quality and quantity. 

And during Rick’s time as CEO, YSI: 

  • Expanded its international presence further, opening additional offices in Baton Rouge, Bahrain, Ireland, Spain, India, and Australia
  • Introduced optical sensors for dissolved oxygen and blue-green algae measurements, along with other new products such as membranes for xylose measurement in biofuels processing, autonomous underwater vehicle for water quality mapping, and multiple-beam acoustic Doppler profilers
  • Released the first wiping system for water quality sondes, significantly extending instrument deployment times
  • Developed a vertical profiling system for high-resolution measurement of water quality throughout a water column
  • Achieved U.S. EPA's Environmental Technology Verification (ETV) after rigorous testing of our instruments
  • Achieved MCERTS certification for multiparameter continuous water quality monitors from the Environment Agency of England and Wales
  • RiverSurveyor M9 was named Most Innovative Product of the Year by the Marine Technology Society
  • Received Third Frontier Grant for the development of new sensor technology from the State of Ohio

Joining the Xylem Family

In September 2011, ITT Corporation purchased YSI and, later that year spun off its water-related businesses into a new publicly-traded company, Xylem (XYL).

YSI, a Xylem brand, continues its legacy of minding the planet – now with the backing of a nearly $5 billion company. Since the acquisition, YSI has benefited from new opportunities for global expansion and the sharing of innovative technology across Xylem's sister brands. But more importantly, we can now provide our customers a more comprehensive solution to better meet their needs.


YSI, a Xlyem brand, is now able to leverage a much broader portfolio of water resource solutions in order to solve water-related issues including quality, transport, treatment, and dewatering.

YSI will continue its legacy of invention and innovation as we move forward; and not just in the area of technology. We will continue to seek creative solutions to support those who use our products and services, ways in which we operate our business, and methods for seeking and retaining talent to continue the mission of our founders. We’ll keep looking for problems to solve through the application of good science.

Looking back on his years with YSI, Trolander said, “I think I am proudest of how we treated our people and the fact when I left the company, 80% of what we made had never been seen until YSI made it.

While Malte opined, “People, people, people. It’s what I cared most about and what I missed the most when I stepped down from the company.


We fully believe and are committed to, minding the planet and supporting our amazing customers throughout the world who are doing it on a daily basis. 

And Rick Omlor celebrated his time with YSI, recalling, “[the company] strived to do something good for the environment. I was drawn to YSI because it’s a bunch of smart people doing some great work. And that’s what got me up in the morning.

It’s what gets all of our employees up in the morning. We’re proud to be a part of a 70 year legacy of scientific innovation.

‘Who’s Minding the Planet?’ Yep. That’s YSI - and you.

Additional Blog Posts of Interest

Icealnd Stream Warming Study Provides a Preview of Climate Change

Voice of Water | Q&A with Philippe Cousteau 

Life After Deepwater Horizon | Remediation Efforts on the Gulf Coast

Waterkeepers at the Third Pole | Protecting the Himalayas

1 Responses to this article

Happy Anniversary!!!!


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