Apera Instruments, AI235, Saltwater Salinity Tester for Aquariums, Aquaculture, Environmental MonitoringAI235 Includes Only:Tester2 AAA Alkaline batteries50 MS/cm calibration solutionCarrying caseFeatures:Dip and test - the easiest way to get reliable saltwater salinity readings (range: 0-100 ppt; accuracy:1.5% of full range)Apera's unique platinum-coated sensor with automatic temperature compensation (32 to 140°F) ensures accuracy and precisionStandardized against the normal standard seawater (s = 35), accurately calibrated in conductivity ratio (K15) and in salinityDesigned for saltwater aquariums, fish farms, and environmental monitoringSingle-button easy operation. Calibration is only needed once a monthThe Apera Saltwater Salinity Tester is designed for easy and reliable salinity measurements for aquariums, aquaculture, and environmental monitoring. Apera's unique platinum-coated sensor with automatic temperature compensation (ATC) ensures accuracy and precision of the measuring results in a wide range -an accuracy of ±1.5% of full range in 0 to 100 ppt (=100,000 ppm).The dip-and-test is the easiest way to get reliable saltwater salinity readings (vs. hydrometers and refractometers). Sampling test is not required. Simply dip the meter into saltwater and get stable readings in 10 seconds. No need for rinsing between each test.Say goodbye to frequent calibration. Calibrating the meter once every month will give you reliable results. The calibration solution is included in the kit. The meter is designed with a single-button operation powered by 2 x AAA batteries. Auto. Power-off and low-battery reminder functions.Note: The Apera tester measures practical salinity (NOT absolute salinity) converted from conductivity using The Practical Salinity Scale 1978 (PSS-78) and is standardized against the Normal Standard Seawater (S=35), which is accurately calibrated in conductivity ratio (K15).