Tungsten filament lamp light source and 90° scattering method, compliant with the U. S EPA 180. 1 method Comes with AMCO high-molecular polymer turbidity standard solutions, which are EPA approved primary standards that are safe, non-toxic and disposable, and have a one-year shelf life. TruRead measurement mode automatically takes multiple consecutive readings, and calculate their average, minimum and maximum value, as well as displaying each set of data in a brief test report. Zero NTU calibration and zero-point error reminder to ensure high accuracy for low-turbidity solutions. Intelligent functions such as automatic calibration, operation navigation, 200 sets of data storage with USB data output to PC (Windows-based), real-time clock display, calibration date check, automatic power off, and low battery reminder.