on the periphery of the turbine. The axial spacing between the rotor and the turbine interposes an axial air gap between the bar and the second magnet when they align. A second sensing coil assembly, that is isolated from the fuel flow, is coaxial with and longitudinally coextensive with the second magnet and the bar. Each time the second magnet passes the bar, the flux that the bar couples to the second sensing coil assembly changes and induces a "stop" voltage pulse in the second sensing coil. As described in the foregoing U.S. Pat. No. 4,056,976, timing circuits convert the start and stop pulses from the first and second sensing coil assemblies into an indication of the mass rate of flow through the meter.
There are, therefore, two separate,mechanical vibrations. These vibrations have radial and axial components that are coupled to the flowmeter and produce corresponding radial and axial forces that act on all the elements in the flowmeter. However, with the construction of the flowmeter, including the methods for mounting the rotor and turbine on a shaft for rotation, the individual elements are more stable in a radial direction than they are in an axial direction and, therefore, are less likely to vibrate in a radial direction.
In addition to vibrationally induced forces, the elements also are subjected to the forces of thermal expansion. When an aircraft is flown, the temperature of the fuel varies widely. Any elements that contact the fuel, including the rotor and the turbine of the flowmeter, are therefore subject to these