TheHanna combo tester combines a high-accuracy pH, EC/TDS, and temperature meter all in one waterproof unit. You no longer have to switch between meters for your routine measurements! The sealed housing protects against humidity and allows the entire unit to float. All pH and EC/TDS readings are automatically temperature compensated. This tester features an easy to read LCD and is equipped with an automatic shut-off. Follow calibration instructions provided in the instruction manual for successful and accurate measuring. These units come calibrated, but you need to clean the meter between readings with a calibration solution. A properly cleaned meter is vital for the most accurate measuring. When you have finished with the unit, rinse the electrode with water to minimize contamination. Add a few drops of storage solution to the protective cap when storing the meter.