The new HANNA digital salinity tester HI98319 has been specially designed to measure salinity in marine aquariums. In simple terms, salinity is the salt content of water, so measuring salinity in marine aquariums is of particular importance. The tester displays values in ppt (parts per thousand), PSU (practical salinity units) or S.G. (specific gravity). The large multi-level display allows one of these units to be displayed simultaneously with the measured temperature inC orF. The stability factor and calibration status can also be read from the LCD. When switched on, the tester displays the current battery level. The waterproof tester uses a built-in amperometric graphite conductivity probe to measure salinity up to 70.00ppt in water, values are automatically temperature compensated by the built-in temperature sensor. The graphite amperometric probe resists oxidation, giving more repeatable readings and is not as susceptible to the polarisation effect as testers using two stainle