YSI Inc, founded in 1948 and based in Yellow Springs, Ohio, is an employee-owned firm that develops environmental monitoring and testing instruments, software, and data collection systems. The company's products measure and monitor water quality, levels, and flow. The systems support ocean, coast, estuary, groundwater, surface water, and aquaculture monitoring and analyses. YSI products and services allow clients to optimize wetlands restoration, deep ocean monitoring, water resource planning, and other operations. The company's systems support the capture and analysis of temperature, salinity, depth, conductivity, dissolved oxygen, chlorophyll, pH, nitrate, phosphate, and other measurement data. The firm also develops biochemical analyzers, monitors, and probes. The systems support bioprocess monitoring, food and beverage processing, and sports physiology operations. The company's first blood-gas analyzer, introduced in the 1950s, provides users with glucose and lactate measurement tools. The firm originally was known for its Model 3A Dielectric Constant meter and for its interchangeable thermistor temperature probes. The company's Model 23 Glucose Analyzer was introduced in the 1970s. The firm introduced its 6-Series environmental monitoring products in the 1990s. YSI provides customers with a variety of laboratory, handheld, and data acquisition instruments. YSI, originally known as Yellow Springs Instruments Company, was founded by Hardy Trolander, John Benedict, and David Jones. Trolander turned over ownership of the firm to employees in 1983. YSI is developing new air and land monitoring systems. The company also operates the nonprofit YSI Foundation.