Apera Instruments TN400 Portable Turbidity Meter is built with an infrared light source, using ISO7207 compliant cephalometric method (90°) with a user-friendly operating system, designed for reliable and easy turbidity measurements from 0 to 1000 NTU in various applications both in-field and in-lab such as water treatment and beverage making. The test kit comes with 4 vials of high-molecular polymer turbidity standard solutions (0. 02 NTU, 20. 0 NTU, 100 NTU, 800 NTU), which are EPA approved primary standard for calibration of turbidity sensors that are safe, non-toxic and disposable; NIST traceable to particle size/distribution and optical density, and its inherent stability means it does not settle from suspension. The standards have a one-year shelf life. The convenient submicron polymer suspensions are non-toxic primary calibration standards approved by the U. S EPA for drinking water analysis. The meter is CE certified and comes with a 2-year .