Hardy W. Trolander

Hardy W. Trolander

Developed medical and environmental measuring and monitoring devices

Enshrined:  2008

Major Field of Study:  Science

Specific Accomplishment:  Developed medical and environmental measuring devices.

Home Town:  Chicago, Illinois

Youth Activities:  Became interested in radio electronics, experimenting with disassembling old radios and building his own with the parts.

Bachelor’s Degree:  Antioch College, Bachelor of Science, Electrical Engineering, 1947

Engineering and Science Achievements:
Trolander co-founded and led Yellow Springs Instruments (YSI)—a firm dedicated to solving technical problems.  They solved many in Trolander’s near-forty-year stint with the company from 1948 to 1986.

  His chief accomplishments included:

  • Inventing the precision interchangeable thermistor (1958), which enabled the use of the thermistor—a type of resistor—in commercial applications for the measurement of medical and biological temperatures.
  • Developing the tele-thermometer (1952), the first practical medical electronic thermometer.  NASA later adopted it for use with astronauts on space flights.
  • Collaborating with Dr. Leland Clark on measuring dissolved oxygen in liquids, which enabled open heart surgery and the first heart-lung machine and which ultimately led to YSI’s development of commercial biosensors.
  • Helping to determine the melting point of gallium, an element used in thermometers that measure high temperature environments.  It’s also used in semi-conductors, transistors, and light-emitting diodes.  In 1990, YSI’s melting point of gallium was adopted as a primary reference point on the international temperature scale.

In addition to developing innovations in medical instruments, YSI eventually branched out into environmental monitoring devices, such as those for measuring water quality and velocity.

Additional Details:

A man of many facets, Trolander was a combination engineer, inventor, businessman, and community leader.  He was very proud of YSI’s personnel policies, which were based on trust and corporate social responsibility.  A YSI employee who met Trolander at a shareholders meeting after the latter had retired described him as a “down-to-earth genuine man” who “shaped the company in the direction of the things that mattered most to him—that everyone was a part of the success, and that companies have a social and ecological responsibility to the community around them.”  Trolander’s and YSI’s commitment to the environment is reflected in the YSI trademarked tagline, “Who’s Minding the Planet?”


Brown, Anita, “Hardy W. Trolander,” The National Academies Press, Memorial Tributes: Volume 19, retrieved 7 February 2017 from https://www.nap.edu/read/21785/chapter/53.

Email from former YSI employee Robert Petrus to the author, 11 February 2017

“Hardy Zobel Trolander,” Yellow Springs News, 31 October 2013, retrieved 11 February 2017 from http://ysnews.com/news/2013/10/hardy-zobel-trolander

Heaton, Lauren, “Hardy Trolander – Minding the Planet,” Dayton Innovation Legacy, retrieved 7 February 2017 from http://www.daytoninnovationlegacy.org/trolander.html.

“The Element Gallium,” Jefferson Lab, retrieved 10 February 2017 from http://education.jlab.org/itselemental/ele031.html

“Who’s Minding the Planet:  The Story of YSI,” excerpts provided in YouTube video, accessed 15 February 2017 at http://www.daytoninnovationlegacy.org/trolander.html

“YSI History,” YSI, retrieved 10 February 2017 from http://www.ysi.com/about/history.