The mass flow of hydrogen fuel in the anode loop of a hydrogen fuel cell is
measured using a rotating flow meter. The flow meter includes a bladed
rotor mounted for rotation within a tube disposed in the stream of
hydrogen fuel flowing through the anode loop. A magnetic sensor senses
changing magnetic field caused by the rotation of the rotor and produces
an alternating signal having a frequency related to the rotational rate of
the rotor, and thus of the mass flow rate of the hydrogen fuel. A fuel
purity sensor increases the accuracy of the mass flow measurement by
determining the concentration of foreign substances contained in the fuel.
