Magnetic material concentration measuring device

A magnetic material concentration measuring device comprising:

• exciting coils to which alternating voltage is applied, the exciting coils being provided on an outer circumference of a flow passage through which a fluid containing a magnetic material flows;
• an output coil from which an alternating voltage signal is output, the output coil being provided in proximity to the exciting coils;
• and a signal processor that obtains a concentration of the magnetic material on a basis of a change in the alternating voltage signal output from the output coil, the magnetic material concentration measuring device comprising:
• a bobbin having an outer circumference around which the exciting coil, the output coil, and the exciting coil are wound;
• an eccentric hole that is eccentrically formed so as to penetrate in an axis line direction of the bobbin;
• a rotor that is rotatably fitted in the eccentric hole about an eccentric axis line;
• a first cutout part that forms a first flow passage on one end side in an eccentric axis line direction of the rotor;
• a second cutout part that forms a second flow passage whose angle is shifted in a rotor rotation direction with respect to the first cutout part, on another end side in the eccentric axis line direction of the rotor;
• and
• a communication passage that is formed in the rotor so as to connect the first flow passage and the second flow passage.