TD-820A Portable Water Quality Tester (COD, Ammonia Nitrogen) Technical Specifications 1. Measuring Range: (Exceeding Dilution Determination) ????COD: 5 ~ 2000mg/L ???? Ammonia Nitrogen: 0.02 ~ 25mg/L2.? Indication error: ????COD: ≤±5?%??????? Ammonia: ≤±3% and 0.2 of the largest 3.?? Repetition: ≤3% 4.?? Optical stability: Absorbance value of the instrument drifts less than 0.002A5 within 20min. Anti-chlorine interference: ≤2000mg/L (COD determination) 6. Weight: 500g