Rapid and accurate determination of chemical oxygen demand of sewage in laboratory and field. It is an essential experimental equipment for environmental monitoring stations, environmental engineering technicians and enterprise laboratories. The function of COD tester is 1. Accurate measurement of COD, ammonia nitrogen, total phosphorus, total nitrogen, turbidity, etc. 2. The instrument comes with 20 standard curves, which can be modified and saved by itself. 3. The instrument can automatically calculate and store 10 regression fitting curves. 4. It can accurately store 4000 measurement results (including measurement time, call curve and numerical value) 5. Print current data and all stored historical data 6. The current data and all stored historical data are transmitted to the computer 7. The digestion temperature is automatically adjusted and controlled according to the load, and the real constant temperature control is realized. Automatic constant temperature reminder, automatic countdown reminder, timing time can be adjusted at will and 9. Three independent timing systems can be saved. Can be operated by three people at the same time (user can choose) 10. It can be extended to an advanced intelligent spectrophotometer, and more than 30 parameters can be measured by photometry. Automatic correction function 12. Large screen LCD display, Chinese interface, Chinese key operation 13. Patent design certificate, technical index parameters of national patented products: measurement range: 10%COD=200mg/L, measurement error: less than 5% Temperature control range: room temperature ~200℃ Measurement time: COD: less than 20min Ammonia nitrogen: less than 20min Total phosphorus: less than 60min Batch sample: 20.