In order to implement the Environmental Protection Law of the People's Republic of China and the Water Pollution Prevention and Control Law of the People's Republic of China, protect the ecological environment, and safeguard human health, the Ministry of Ecology and Environment issued the "Technical Specifications for Installation of Online Monitoring Systems for Water Pollution Sources (CODCr, NH3-N, etc.)" and "Technical Specifications for Acceptance of Online Monitoring Systems for Water Pollution Sources (CODCr, NH3-N, etc.)" on December 24, 2019. In the "Installation Technical Specification", it is proposed that a flow monitoring unit is required in the composition of the online monitoring system. For the discharge units that need to measure flow, standardized measuring weirs (troughs) should be built for open channels, and the construction of weirs should be able to compare open channel flow meters. Triangular weirs, rectangular weirs, and Bacher troughs are recommended. In the "Acceptance Technical Specification", specific requirements are proposed for the acceptance method of water pollution source flow monitoring units, which are divided into liquid level error comparison and flow error comparison, as follows:

(1) Liquid level error comparison: Use a portable open channel flow meter comparison device and an ultrasonic open channel flow meter to measure the liquid level values at the same water level observation section, conduct a comparison test, record the data pairs every 2 minutes for 6 consecutive times, calculate the error value Hi of each data pair, and select the maximum Hi as the liquid level comparison error of the flow meter.

(2) Flow Error Comparison: Use a portable open channel flow meter comparison device and an ultrasonic open channel flow meter to measure the instantaneous flow at the same water level observation section for comparison experiments. After the data is stable, start timing for 10 minutes. Read the cumulative flow F1 of the open channel flow comparison device and the cumulative flow F2 of the ultrasonic open channel flow meter during this period, and calculate the flow comparison error Δ F according to the formula.

According to the above requirements, it can be seen that portable open channel flow meters are needed for on-site acceptance. During the acceptance process, continuous statistics and recording of liquid level data and flow data are required. It is necessary to synchronously record 6 liquid level data each from the online open channel flow meter and portable sewage flow meter within 12 minutes, and 2 accumulated flow data each from the online open channel flow meter and portable sewage flow meter within 10 minutes. Moreover, because the sewage flow monitoring process is irreversible, once problems occur during the recording process, it is necessary to re compare and accept, which brings difficulties to the on-site acceptance work in terms of time and space.

Although there are various types of open channel sewage flow meters in China, there is no portable sewage flow meter that can easily and quickly complete the above acceptance tasks. Our company has developed a HX-F3 portable open channel flow meter specifically for the on-site acceptance requirements of open channel flow meters, based on years of experience in environmental monitoring instrument research and development, combined with the requirements of the "Technical Specifications for Installation of Online Monitoring Systems for Water Pollution Sources (CODCr, NH3-N, etc.)" and "Technical Specifications for Acceptance of Online Monitoring Systems for Water Pollution Sources (CODCr, NH3-N, etc.)".