Nitrites are an intermediate product in the nitrogen cycle and are produced by ammonia oxidation with water, or even originate in industrial waste directly. They must not be present in drinking water. This meter uses an exclusive positive-locking system to ensure that the cuvette is in the same place every time it is placed into the measurement cell. Cal Check. User calibration. Certified calibration and verification standards. BEPS (battery error prevention system). Timer function. Auto shut-off. GLP Features. Range: 0 to 150 milligrams per liter. Resolution: 1 milligrams per liter. Accuracy: +/-4 milligrams per liter +/-4 percent of reading at 25 degree celsius. Light source: tungsten lamp. Light detection: silicon photocell with narrow band interference filter at 575 nm. Battery type/life: 9V/approx. 40 hours of continuous use; auto-off after 10 minutes of non use. Environment: 0 to 50 degree celsius (32 to 122 degree fahrenheit); RH max 95 percent non-condensing. Measures 7-19/32" length by 4-3/32" width by 2-11/16" height. Method: adaptation of the ferrous Sulfate method; The reaction between nitrite and the reagent causes a greenish-brown tint in the sample.