YSI's first success was an innovative crystal clock, sold to the Air Force. Today, the company is a global player, with 380 employees around the world and revenues of about $100 million. And while it has demonstrated expertise in a number of sensor applications over the years, it now focuses on the natural resource water market. In other words data collection for ponds, oceans, rivers and streams.The company says demand for YSI products differ around the world. China has emerged as a prime source for YSI products, but a variety of markets are concerned about water quality, water velocity and water quantity. The company employs 130 at its Yellow Springs headquarters.