Electromagnetic flow meter including a function of measuring electrical conductivity of a fluid

An electromagnetic flow meter comprising:

• a measurement tube which is formed of an electrical insulation material and through which a measurement target fluid flows;
• a magnetic excitation coil which is disposed outside the measurement tube and generates a magnetic field according to a supplied AC current having a first frequency;
• a first electrode and a second electrode which are provided on an outer peripheral surface of the measurement tube and are disposed opposite to each other in a direction perpendicular to the magnetic field generated from the magnetic excitation coil;
• an amplifying circuit that operates with a common potential as a reference and outputs a signal obtained by amplifying an electromotive force generated between the first electrode and the second electrode;
• a flow rate calculation portion that calculates a flow rate of the measurement target fluid based on a signal output from the amplifying circuit;
• a third electrode which is formed on the outer peripheral surface of the measurement tube to be separated from the first electrode and the second electrode;
• a fourth electrode which is connected to the common potential and is in contact with the measurement target fluid;
• a resistor of which one end is connected to the third electrode;
• an AC signal generator connected to another end of the resistor, the AC signal generator being adapted to generate an AC signal having a second frequency that is different from the first frequency;
• a voltage detecting circuit that measures voltages of a signal generated in the third electrode while the AC signal is generated at and input to the another end of the resistor;
• and
• an electrical conductivity calculating portion that calculates an electrical conductivity of the measurement target fluid based on an amplitude of the voltages measured by the voltage detecting circuit.