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An electromagnetic flow meter for measuring the flow rate of a
fluid by applying to the fluid a magnetic field generated with an
exciting current and measuring the resulting signal voltage generated
at a pair of electrodes; wherein the exciting current comprises
two frequency components which are lower and higher than the usual
commercial frequency and the signal voltage comprises two frequencies
which are discriminated so that a higher frequency is extracted
as a first output and a lower frequency is extracted as a second
output, through a low pass filter having a large time constant.
A predetermined operation, such as addition, zero correction, response
correction, etc, is carried out on the first and second outputs
to produce a flow rate output. The invention has quick response,
stable zero point and reduced susceptibility to noises.
A flow meter includes a flow channel having walls and defining
a direction of flow. Stators are provided, having walls, disposed
at least partially within the flow channel. A rotor is included
for rotating with respect to the stator. A one piece retainer is
provided for assisting in limiting axial rotor movement comprising
a first pair of spaced apart wall portions for engaging the flow
channel walls wherein each wall portion in the first pair of wall
portions is located on a side of an axis opposite from the other.
A second wall portion is located on the axis for engaging the stator
wall wherein compression of each of the first pair of wall portions
toward the axis results in a component of force being applied to
the second wall portion along the axis.
A mass flow meter operating by the Coriolis principle comprises
a mechanical oscillating system having two straight measuring tubes
which are clamped at both ends. The mechanical oscillating system
is arranged axially in a support tube. In the center of the measuring
tubes an oscillation exciter is disposed which sets the two measuring
tubes into oppositely phased flexural oscillations. Oscillation
sensors sensing the mechanical oscillations at equal distances on
both sides of the oscillation exciter generate electrical oscillation
sensor signals which are characteristic of the frequency and phase
position of the sensed oscillations. An evaluation circuit receives
the oscillation sensor signals and generates from their phase difference
a measuring signal indicating the measured value of the mass flow.
A first temperature sensor is arranged such that it measures the
temperature of the support tube and generates a first temperature
sensor signal indicating said temperature. A second temperature
sensor is so arranged that it measures the temperature of the mechanical
oscillating system and generates a second temperature sensor signal
indicating said temperature. A correction circuit receives the two
temperature sensor signals and imparts to the measuring signal on
the basis of the temperatures measured a correction for eliminating
the temperature influence on the measurement result.
A mass flow meter based on the Coriolis principle. The meter has
two rectilinear measuring tubes juxtaposed in parallel and mechanically
connected at adjacent ends thereof. An oscillation generator is
connected to the tubes between the ends thereof for driving the
tubes in opposite directions. A sensor connected to the tubes on
opposite sides of the oscillation generator sense and signal relative
oscillations of the tubes which is indicative of the flow through
the tubes. The measuring tubes have different bending strengths
in two perpendicular axial planes thereof to reduce the amplitudes
of vibration in the plane normal to the plane of interest. Individual
masses applied to the measuring tubes cause the natural frequency
of at least the first mechanical harmonic of the measuring tubes
to differ from the natural frequency of the mechanical fundamental
counter-oscillation by a factor x which differs from a whole number
by at least 0.1.
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