Introduction Section 1
YSI Incorporated Environmental Monitoring Systems Manual 1-1
SECTION 1 INTRODUCTION
1.1 ABOUT YSI INCORPORATED
From a three-man partnership in the basement of the Antioch College science building in 1948, YSI has
grown into a commercial enterprise designing and manufacturing precision measurement sensors and
control instruments for users around the world. Although our range of products is broad, we focus on three
major markets: water testing and monitoring, health care, and bioprocessing.
In the 1950s, Hardy Trolander and David Case made the first practical electronic thermometer using a
thermistor. This equipment was developed to supply Dr. Leland Clark with a highly sensitive and precise
temperature sensor for the original heart-lung machine. The collaboration with Dr. Clark has been critical
to the success of the company. In the 1960s, YSI refined a Clark invention, the membrane covered
polarographic electrode, and commercialized oxygen sensors and meters which revolutionized the way
dissolved oxygen was measured in wastewater treatment plants and environmental water. Today,
geologists, biologists, environmental enforcement personnel, officials of water utilities and fish farmers
recognize us as the leader in dissolved oxygen measurement.
In the 1970s, YSI again worked with Clark to commercialize one of his many inventions, the enzyme
membrane. This development resulted in the first practical use of a biosensor, in the form of a membrane
based on immobilized glucose oxidase, to measure blood sugar accurately and rapidly. In the next few
years, this technology was extended to other enzymes, including lactate oxidase, for applications in
biotechnology, health care, and sports medicine.
In the early 1990s, YSI launched a line of multi-parameter water monitoring systems to address the
emerging need to measure non-point source pollution. Today we have thousands of instruments in the field
that operate with the push of a button, store data in memory, and communicate with computers. These
instruments (described in this manual) are ideal for profiling and monitoring water conditions in industrial
and wastewater effluents, lakes, rivers, wetlands, estuaries, coastal waters, and monitoring wells. If the
instrument has ‘on board’ battery power, it can be left unattended for weeks at a time with measurement
parameters sampled at the user’s setup interval and data securely saved in the unit's internal memory. The
fast responses of YSI’s sensors make the systems ideal for vertical profiling, and the small size of some our
sondes allows them to fit down 2-inch diameter monitoring wells. All of YSI’s multi-parameter systems
feature either the YSI-patented Rapid Pulse Dissolved Oxygen Sensor, which exhibits low-stirring
dependence and provides accurate results without an expensive, bulky, and power-intensive stirrer or an ROX
optical dissolved oxygen sensor which exhibits no flow dependence and is extremely stable in long-term
deployments.
YSI has established a worldwide network of selling partners in over 50 countries that includes laboratory
supply dealers, manufacturers' representatives, and YSI’s sales force. A subsidiary, YSI UK, distributes
products in the United Kingdom, a sales office in Hong Kong supports YSI’s distribution partners in Asia
Pacific, and YSI Japan supports distribution partners in Japan.
Through an employee stock ownership plan (ESOP), every employee is one of the owners. In 1994, the
ESOP Association named YSI the ESOP Company of the Year. YSI is proud of its products and are
committed to meeting or exceeding customers' expectations.
1.2 HOW TO USE THIS MANUAL
The manual is organized to let you quickly understand and operate the YSI 6-Series environmental
monitoring systems. However, it cannot be stressed too strongly that informed and safe operation is more
than just knowing which buttons to push. An understanding of the principles of operation, calibration
