5. Two forms of pneumatic control valve FO
A: The air source enters the upper chamber of the membrane chamber, the spring is located in the lower chamber of the membrane chamber, the valve core is installed, and the valve is closed after air intake.
B: The air source enters the lower chamber of the membrane chamber, the spring is located in the upper chamber of the membrane chamber, the valve core is reversely installed, and the valve is closed after air intake.

2、 Problems of fluid conductivity
The decrease of fluid conductivity will increase the output impedance of the electrode, and the error will be caused by the load effect caused by the input impedance of the converter. Therefore, the lower limit of fluid conductivity in the application of electromagnetic flowmeter is specified according to the following principles.