【Salinity Refractometer】 Measure Salt Water or Salinity of Water, Monitor and Control the Concentration of Salt Water and Brine, Ideal for Aquariums and Marine Applications 【Measures on 2 Scales】 Specific Gravity (D 20/20) and parts per thousand and replaces your poor quality and difficult-to-read hydrometer 【Density Measurement Range】 1.0-1.070, Minimum Scale is 0.001 【Concentration Measurement Range】 0-100‰, Minimum Scale is 1‰ 【ATC】 Automatic Temperature Compensation, 0-10 °C; ① It is necessary to keep the surrounding environment with sufficient brightness and a suitable temperature during use. There is no error when the temperature is 10-30 ℃. If it deviates from this temperature, there will be a certain error. ② Because people’s focal lengths are different, reverse rotation may be necessary when focusing