A contact free flow meter for determining the velocities and/or
flow directions of electrically-conductive fluids is disclosed.
At least one primary magnetic field is arrayed generally perpendicular
to the flow path, the field having strength gradients extending
along the flow path. At least two magnetic field sensors are spaced
apart in the direction of the flow path the sensor being responsive
to the magnetic field. The device is capable of functioning notwithstanding
electrically-conductive material such as pipe walls interposed between
the fluid and the meter.
Having thus described the invention and illustrated its use, what
is claimed as new and is desired to be secured by Letters Patent
1. A flow meter for contact-free measurement of flow velocity of
electrically conductive fluid media using the interaction between
at least one magnetic field and non-homogeneous or non-stationary
patterns of fluid flow comprising a conduit defining a fluid flow
path, means for generating a magnetic field in said flow path, said
field extending substantially perpendicular to said path, said field
including at least one gradient in said flow path of said fluid
and at least two magnetic field measuring means mutually spaced
apart along said flow path downstream of said field for measuring
said gradient field in a direction generally perpendicular to said
2. A flow meter in accordance with claim 1 wherein said magnetic
field producing means comprise a permanent magnet or a coil.
3. A flow meter in accordance with claim 1 wherein said conduit
comprises magnetically conductive material.
4. A flow meter in accordance with claim 1 wherein said means for
generating a magnetic field comprise a series of magnets on a side
of said conduit, said magnets being mutually spaced along said flow
5. A flow meter in accordance with claim 4 and including two or
more magnetic field measuring means positioned to sense the field
gradient of each of said series of the magnets which comprise magnets.
6. A flow meter in accordance with claim 5 and comprising readout
means including a plotter for displaying the output of said field
7. A flow meter assembly for measuring flow velocity and flow direction
of an electrically conductive fluid media within an enclosure using
the interaction between a magnetic field and non-homogeneous or
non-stationary patterns of fluid flow, comprising a conduit divider
within said enclosure, first and second angularly offset flow meters
within said enclosure, each said flow meter comprising a conduit
defining a fluid flow path, means for generating a magnetic field
in said flow path, said field extending substantially perpendicular
to said path and including at least one gradient along the flow
path of said fluid within said conduit, and at least two magnetic
field measuring means spaced apart along said flow path downstream
of said field generating means for measuring said field in a direction
generally perpendicular to said flow path.
The present invention relates to a flow meter for contact-free
determination of velocities of electrically conductive fluid media.
The device makes use of the interaction between at least one primary
magnetic field and non-homogeneous or non-stationary flow fractions.
The fluid is passed through at least two magnetic field measuring
devices, so that the flow velocity and/or direction can be determined
Aside from generally known devices for measurement of local flow
velocities which rely on measurement probes inserted into the flowing
media, an inductive probe flow measurement system is known from
DE 33 47 190 A1 that facilitates contact-free determination of the
velocities of electrically-conductive fluid media. A transformer
coupling of three cylindrical induction coils is altered by the
flowing medium, and a signal dependent on flow velocity is obtained
Although in the known inductive-probe flow-measurement system,
the transformer coupling of the coils is amplified by ferromagnetic
coil cores and thus facilitates measurements through thicker cladding
tubes, this system suffers from a significant disadvantage. This
consists in the fact that the transformer coupling is influenced
not only by the flow velocity of the medium, but also, for example,
by the current conductivity and temperature of the surroundings,
necessarily resulting in measurement errors.
A further arrangement is known from DE 33 26 476 A1 that, among
other things, serves to determine the quantity of motion of an object
that can alter an alternating magnetic field by its action. Different
localized magnetic field sensors are arranged in the area of influence
of the alternating magnetic field. The magnetic field sensor output
signals allow recognition of the impact on the alternating magnetic
field caused by the object to be measured.
The fact that the signals output by the magnetic field sensors
are independent of the velocity of the object to be measured is
touted as a significant advantage of this known arrangement. The
device, however, suffers from a major disadvantage, namely, with
the exclusive use of alternating fields, no components, e.g. walls,
of an electrically-conductive material may be placed between the
measuring device, on the one hand, and the body to be measured,
on the other, in order to be able to make a sufficiently precise
Finally, in printed document "EUR 6296 DE I" of the European
Communities Commission, "Technical Research--Steel--Measurement
and Analysis--Measurement of Flow of Liquid and Solid Metal",
a measurement device is described (pp 22 and ff.) and shown as a
diagram (pp. 55 and ff.), according to which a homogeneous alternating
field is used to measure the velocity of liquid metal as the primary
field. The alternating effect of the primary field, however, can
be used with the flow only on a very contingent and spatially inaccurate
SUMMARY OF THE INVENTION
The invention has for it primary object creating a flow meter of
the magnetic field type in such manner that the velocities and/or
directions of electrically-conductive fluid media can be determine
precisely, despite the existence of walls, consisting of or containing
electrically-conductive material interposed between the flow meter
and the media.
To attain this object there is provided a contact-free flow measuring
device for non-homogeneous or moving electrically conductive fluids,
the device including means for conducting the fluid along a predetermined
path, at least one primary magnetic field forming device for generating
a field perpendicular to the path, the field having a gradient in
the flow direction, and at least two magnetic field measuring components
encompassed within the field and separated in the direction of movement
of the flow of fluid for measuring the field in a direction perpendicular
to the flow direction.
This electrically-conductive component, can, without losses, penetrate
the primary field, formed as a direct current field, pursuant to
the invention. By adjustment of the field produced, the devices
which measure the magnetic fields can lie at the point of maximum
interaction between the primary field and the non-homogeneous or
non-stationary flow fraction and thus in the range of maximum magnetic
field alteration. The simultaneous use of several components measuring
magnetic fields makes it possible to effectively eliminate from
the evaluation signal fractions not caused by motion, e.g. by correlation.
The flow meter pursuant to the invention thus permits not only measurement
of motion velocity and direction of the medium through walls of
electrically-conductive components but also permits the placement
of the meter at a greater distance from the flowing medium, without
impairing the precision of the measurement results. The simultaneous
use of several components measuring magnetic fields also permits
determination of flow direction.
According to the methods of embodiment of the invention, the components
producing magnetic fields may consist of coils or permanent magnets,
and may be arranged on a side, facing the electrically-conductive
fluid medium, of a carrier made of magnetically-conductive material.
The carrier of magnetically-conductive material may, for example,
be a yoke that defines spatial areas in which the primary field
According to a further method of embodiment of the invention, several
component producing and measuring magnetic fields form components
combinations that are arranged in such manner that simultaneous
measurement of the velocity components is possible in different
Finally, a method of embodiment of the invention provides that,
with one or more of the components measuring magnetic fields, one
or more electronic reader and/or plotter and/or amplifier units
are placed in a common housing.
It may also be advantageous to apply the components measuring and
producing magnetic fields in or on a wall or at a distance therefrom
whereby the wall may be a component of a container or a conduit.
Naturally, insulating and/or cooling the components producing and
measuring magnetic fields and/or the electronic reader or plotter
unit as necessary from the effects of heat also falls within the
framework of the invention.
BRIEF DESCRIPTION OF DRAWINGS
A flow meter pursuant to the invention is shown in the drawings.
FIG. 1 a schematic representation of the meter arranged on an extended
FIG. 2 a schematic representation of the meter arranged on a conduit
DETAILED DESCRIPTION OF DRAWINGS
The portion of conduit 1 shown in part, serves to allow the flow
of an electrically-conductive fluid medium, the velocity of which
is to be measured.
The medium flows through a magnetic field produced by components
2 e.g. permanent or electromagnets, arranged on the exterior of
conduit 1 the components being spaced along the conduits to provide
gradients. Dotted line 3 that runs perpendicular to the longitudinal
axis of conduit 1 between adjacent magnetic field producing components
2 indicates the planes where the gradients reach their maxima. In
these planes, components 4 comprising field strength measuring
devices, are arranged on the exterior of conduit 1 facing the side
of conduit 1 having the field producing devices 2. Signals from
components 4 are forwarded to plotter unit 5 for example.
The interaction of a non-homogeneity in the flowing medium with
the magnetic field produced occurs successively in all components
4 measuring magnetic fields, so that the velocity can be determined
directly from their distance from each other and the time interval
between successive signals.
The arrangement pursuant to FIG. 2 facilitates measurement of velocity
components in various spatial directions. If, pursuant to this method
of embodiment, a medium flows over supply conduit 6 of conduit divider
7 and out through attached outlet conduits 8 and 9 set at right
angles to each other, the velocity components X in conduit divider
7 can be determined by component combination 10 and velocity component
Y can be determined by additional component combination 11 each
of which includes field producing and plural field sensing devices
2 and 4. Component combinations 10 and 11 are arranged in such manner
that several components act simultaneously to determine both the
velocity for the X direction and the velocity for the Y direction.
From the foregoing, it will appreciated that there is provided,
in accordance with the invention, a fluid flow measuring device
for conductive fluids which will function without contacting the
fluid and which will operate notwithstanding conductive components
such as tube walls or the like intervening between the fluid and
the measuring device.