The present invention provides a device for generating an electrical
output signal representative of the flow rate through a fluid flow
meter of the type having a mechanical output member movable in an
amount proportional to the fluid flow rate. The device comprises
the U-shaped magnet having a north and south pole and a Hall effect
transducer positioned between the poles of the magnet. The transducer
produces an electrical signal representative of the distance between
the transducer and one of the magnetic poles. The magnet in turn
is connected to the mechanical output member from the flow meter
so that the magnet moves in unison with the output member from the
flow meter thus varying the transducer electrical output. The output
from the transducer is electrically connected to a conventional
electrical indicator to produce an indication of the fluid flow
rate through the flow meter.
1. For use in conjunction with a fluid flow meter having a mechanical
output member movable in an amount proportional to the fluid flow
rate through the flow meter, a device for generating an electrical
output representative of the flow rate through the flow meter comprising:
a magnet having a north and south pole,
a transducer positioned between said poles of said magnet, said
transducer producing an electrical signal representative of the
distance between the transducer and one of said poles, and
means for moving said magnet to vary the distance between said
one of said poles with respect to said transducer in a direction
opposite to movement of the other of said poles with respect to
said transducer in an amount proportional to the movement of said
mechanical output member from the flow meter.
2. The invention as defined in claim 1 wherein said electrical
signal comprises a variable voltage signal.
3. The invention as defined in claim 2 and comprising means for
converting said voltage signal to a current proportional to said
4. The invention as defined in claim 1 wherein said moving means
comprises means for mechanically connecting the output member to
5. The invention as defined in claim 4 wherein the output member
rotates an amount proportional to the flow rate and wherein said
mechanical connecting means comprises
a pinion secured to the output member,
a gear rack secured to the magnet, and
wherein said pinion meshed with said gear rack.
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to electrical indicating means for
use with a fluid flow meter.
II. Description of the Prior Art
There are a number of previously known fluid flow meters having
a rotatable output shaft which rotates in an amount proportional
to the fluid flow rate through the flow meter. Typically, an indicator
needle is secured to the shaft and cooperates with an indicia scale
on the flow meter to provide a visual indication of the fluid flow
One disadvantage of these previously known fluid flow meter indicators
is that the fluid flow rate of the flow meter can not be monitored
from a position remote from the flow meter. Instead, the meter must
be visually inspected in order to determine the flow rate. This
procedure, however, is particularly disadvantageous in situations
where it is desirable to monitor a plurality of flow meters from
a central control area.
There have, however, been a number of previously known fluid flow
meter indicator devices which produce an electrical signal representative
of the flow rate from the flow meter. These electrical outputs can
then be read at a position remote from the flow meter itself. One
disadvantage of these previously known devices, however, is that
they are expensive in construction and prone to failure.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a fluid flow meter indicator which
overcomes all of the above mentioned disadvantages of the previously
In brief, the indicator device of the present invention comprises
a U-shaped magnet having a north and south pole. In the preferred
form of the invention, a rack is secured to the magnet and cooperates
with a pinion attached to the output shaft from the flow meter.
Consequently, rotation of the flow meter output shaft linearly displaces
the magnet along a predetermined path of travel.
A Hall effect transducer is positioned between the magnetic poles
of the magnet. The Hall effect transducer produces a voltage output
representative of the distance between the transducer and one of
the magnetic poles. A voltage to current converter then translates
the voltage output from the transducer to a current signal proportional
to the position of the magnet and thus of the fluid flow rate through
the flow meter. The output from the converter is connected to a
conventional electrical indicator which can be at a position remote
from the flow meter .
BRIEF DESCRIPTION OF THE DRAWING
A better understanding of the present invention will be had upon
reference to the following detailed description, when read in conjunction
with the accompanying drawing wherein like reference characters
refer to like parts throughout the several views, and in which:
FIG. 1 is a diagrammatical view illustrating a preferred embodiment
of the invention; and
FIG. 2 is a diagrammatic view taken substantially along line 2--2
in FIG. 1 .
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
With reference to the drawing, a preferred embodiment of the indicating
device of the present invention is thereshown for use with a conventional
fluid flow meter 10. The fluid flow meter 10 which is illustrated
only diagrammatically, includes a fluid inlet 12 and a fluid outlet
14. The flow meter 10 can, for example, comprise a piston-type flow
meter and includes an output shaft 16 which rotates an amount proportional
to the fluid flow rate from the inlet 12 and to the outlet 14.
The preferred embodiment of the indicating device of the present
invention comprises a U-shaped permanent magnet 18 having a north
pole 20 and a south pole 22. A track assembly 24 (illustrated only
diagrammatically) allows the magnet 18 to move linearly in a direction
parallel with its base 26.
A pinion 28 is secured to the flow meter output shaft 16 and meshes
with a gear rack 30 secured to the magnet base 26. Consequently,
the rack 30 and pinion 28 translate the rotational motion of the
shaft 16 to linear motion of the magnet 18.
With reference now particularly to FIG. 2 a Hall effect transducer
32 is positioned at a midpoint between the magnet poles 20 and 22.
The transducer 32 generates a voltage at its output 34 having a
magnitude representative of the distance between one of the magnetic
poles 20 or 22 and the transducer 32. Consequently, the voltage
on the transducer output 34 will vary as the magnet 18 is moved
from the position shown in phantom line and to the position shown
in solid line, and vice versa.
The output 34 from the transducer 32 is, in turn, connected as
an input signal to a voltage-to-current converter 36. The converter
36 generates a current signal at its output 38 which is proportional
to its voltage input. In the preferred form of the invention, the
converter generates an output current of four milliamps when the
magnet 18 is in one extreme position and increases to a current
output of 20 milliamps when the permanent magnet 18 is in its other
Still referring to FIG. 2 the current output 38 from the converter
36 is connected as in input signal to an indicator 40 which can
be of any conventional design. Furthermore, the indicator 40 can
be physically located at a place remote from the flow meter 10.
From the foregoing, it can be seen that the present invention provides
a simple, inexpensive and yet totally effective device for converting
the mechanical output from a flow meter to an electrical signal
which can be monitored at a position remote from the flow meter.
Consequently, the present invention enables a plurality of spaced
apart flow meters to be monitored at a central control area.
Although the preferred embodiment of the invention uses a rack
and pinion for translating the mechanical rotary output from the
flow meter to linear movement of the magnet, it will be understood
that other means may alternatively be used.
Having described my invention, however, many modifications thereto
will become apparent to those skilled in the art to which it pertains
without deviation from the spirit of the invention as defined by
the scope of the appended claims.