The Signet 2507 Mini Flow Sensor contains a free-running
rotor that is driven by the fluid flow. Within the given
measurement range, the rotational speed of the rotor is
proportional to the fluid flow rate. Permanent magnets built
into the rotor actuate an electronic switch in the top of the
sensor generating a square-wave output signal proportional to
flow rate. Both opaque and transparent fluids can be measured
from 0.2 to 20.0 centistokes.