YSI Hydrodata is a wholly owned subsidiary of YSI Inc, manufacturers of water quality testing and monitoring instruments and systems YSI water quality meters and multiparameter water quality sondes are market leaders all over the world with a reputation for high levels of accuracy and reliability. YSI's water quality measuring instruments are designed for laboratory and field use - for example, a full range of lab test meters are avialable in addition to hand held water quality testing devices that can also be used for testing streams, rivers, reservoirs, boreholes etc. Thousands of YSI multiparameter water quality sondes are in regular use, either as portable measuring instruments, or in a fixed location recording data to the sondes's own internal datalogger. These sondes can be fitted with a wide variety of water quality, level and flow sensors including DO (dissolved oxygen), pH, temperature, turbidity, EC (conductivity), salinity, ORP, chlorophyll, open-channel flow, velocity, vented level, nitrate-nitrogen, ammonium-nitrogen, ammonia, chloride, rhodamine, depth, light, PAR (photosynthetically active radiation). YSI also builds water quality monitoring systems and wireless networks that record data on internal loggers and transmit the water quality data via satellite, gsm, cellphone, or radio. Alternatively, data collection staff can download readings during routine visits to the water quality monitoring station. Water quality sondes can be mounted in the point of greatest water quality interest, such as close to a discharge, on the river or sea bed, or mounted on a buoy for surface water quality measurements.