② Valves: valves are the control parts in the fluid transmission system (including ball valves, butterfly valves, stop valves, gate valves, control valves, etc.).

For the fluid with substances easy to adhere, deposit and scale, the flow rate shall not be less than 2 m/s, and it is better to increase it to 3~4 m/s or above, so as to play the role of self-cleaning and preventing adhesion and deposition. For slurry and other highly abrasive fluids, the common flow rate should be lower than 2~3m/s to reduce the wear of lining and electrode. When measuring the low conductivity liquid close to the threshold value, select a lower flow rate (less than 0.5~1m/s) as far as possible. As the flow rate increases, the flow noise will increase, resulting in output shaking.