DiST's are rugged and reliable pocket-sized testers that offer quick and accurate readings of conductivity or TDS. The DiST family of testers is widely used for monitoring EC/TDS in drinking water, water conditioning, reverse osmosis, cooling towers, wastewater, laboratories, agriculture, aquaculture and aquariums, hydroponics and the printing industry. This tester features an amperometric graphite electrode that provides better repeatability in measurements since they do not oxidize. An amperometric measurement of TDS is based on Ohm's Law, I = V/R where R depends on the distance between two pins and their surface. Oxidation changes both the distance and surface which will affect accuracy. The DiST's non-oxidizing graphite pins are able to provide an optimal surface for accurate, dependable results. When calibration is necessary, simply submerge the electrode tip into calibration solution and adjust the trimmer on the side of the tester. Range: 1999 ppm ( milligrams per liter). Resolution: 1 ppm ( milligrams per liter). Accuracy: +/-2 percent F.S. TDS Factor: 0.5. Calibration Solution: HI70442. Calibration: manual, 1 point. Probe: HI73301. Temperature Compensation: automatic, 0 to 50 degree C (32 to 122 degree F). Battery Type/Life: 1.5V (4)/approximate 200 hours of continuous use. Environment: 0 to 50 degree C (32 to 122 degree F); RH max 95 percent. Weight: 3.4 oz. Measures 1-19/32" length by -57/64" width by 6-57/64" height.