This dissolved oxygen meter offers LCD digital readout and many other special features for excellent performance in both lab and field environments. The Model 58 digital meter has been expressly designed for high readability in natural or artificial light. In field use, the gasketed ABS case is water resistant when both recorder output and battery eliminator receptacles are capped. This instrument offers the most accurate salinity correction of any instrument YSI makes --- direct-dial salinity compensation from 0 to 40 PPT is temperature-compensated. Actual salinity concentration can be measured with companion instruments, such as the YSI Model 33 S-C-T Meter. Dissolved oxygen can be measured with two resolutions --- 0 to 20.0mg/L and 0.01 mg/L, accurate to 0.01mg/L. The instrument also measures % air saturation from 0 to 200.0%, accurate to 0.1%. Temperature is measured from 5 to 45C, accurate to 0.3C. The Model 58 can also measure % air saturation in gases as well as in certain other liquids. A selector switch in the instrument case permits direct reading with any YSI membrane: standard (1 mil), high sensitivity (0.5 mil) or half sensitivity (2 mil).