Selection precautions:

1. The accuracy level and function of the instrument are selected based on measurement requirements and usage scenarios to achieve economic benefits. For example, when used for trade settlement, product handover, and energy measurement, higher accuracy levels such as 1.0, 0.5, or higher should be chosen; For process control applications, select different accuracy levels according to control requirements; In some cases where only the process flow is detected without the need for control and measurement, slightly lower accuracy levels such as 1.5, 2.5, or even 4.0 can be selected. In this case, low-cost plug-in open channel flow meters can be used.

2. When measuring medium flow velocity, instrument range, and diameter, the full flow rate of an open channel flowmeter can be selected within the range of 0.5-12m/s for measuring medium flow velocity, which is relatively wide. The selection of instrument specifications (caliber) may not necessarily be the same as the process pipeline. It should be determined based on whether the measured flow rate range is within the flow rate range. That is, when the pipeline flow rate is too low to meet the requirements of the flow instrument or the measurement accuracy cannot be guaranteed at this flow rate, it is necessary to reduce the instrument diameter to increase the flow rate inside the pipeline and obtain satisfactory measurement results.

3. Fluid characteristics mainly refer to the pressure, temperature, density, viscosity, compressibility, etc. of gas. As the volume of gas changes with temperature and pressure, compensation and correction should be considered.

4. Instrument performance refers to the accuracy, repeatability, linearity, range ratio, pressure loss, initial flow rate, output signal, and response time of an instrument. When selecting a flow meter, the above indicators should be carefully analyzed and compared, and an instrument that can meet the requirements of measuring medium flow rate should be selected.

5. Installation conditions refer to the flow direction of gas, pipeline direction, length of upstream and downstream straight pipes, pipe diameter, spatial position, and fittings, all of which can affect the accurate operation, maintenance, and service life of gas flow meters.

6. Economic factors refer to procurement costs, installation costs, maintenance costs, calibration costs, and spare parts, which are also affected by the performance, reliability, and lifespan of gas flow meters.