VIBRATINGFLOW METER AND METHOD FOR MEASURING
TEMPERATURE
Background of the Invention
1. Field of the Invention
The present invention relates to a vibrating flow meter and method, and more
particularly, to a vibrating flow meter and method for measuring temperature.
2. Statement of the Problem
Vibrating flow meters can be affected by various operational factors. One
environmental factor that can affect the accuracy of a vibrating flow meter is
temperature. This can include the temperature of the flow material. This can further
include the temperature of the meter environment, such as the surrounding air and the
conduits connected to the flow meter, for example.
A vibrating flow meter is typically designed and calibrated for operation at an
expected temperature or range of temperatures. Deviation from an expected temperature
or range of temperatures can affect measurements made by the flow meter. For
example, the stiffness of the flowmeter structure is affected by temperature and can
affect mass flow rate measurements. In addition, changes in temperature can affect a
resonant frequency of the vibrating flow meter.
Temperature effects can be compensated for in the flow meter. A typical
temperature compensation approach in the prior art is to affix a temperature sensor to
the side of the flowmeter conduit and use a temperature measurement to scale meter
output in a known manner. This can include temperature compensation for changes in
elastic modulus i the meter structure due to changes in temperature, where the resonant
frequency of the meter may change with temperature. The typical straight tube meter
might also require a temperature sensor on the balance structure and/or the case. The
difference between the balance /case temperature and the flow conduit temperature is
used for.compensation for thermal stress (i.e., tension or compression forces) due to
changes in temperature, wherein physical dimensions of the meter may change.
FIG. 1 depicts a single conduit type vibrating flow meter according to the prior
art. As shown, the f ow meter includes a case 103 enclosing a balance bar 02. The
balance bar 102 is cylindrical and encloses conduit 101. Case 103 has end elements 104
coupled by neck elements 105 to input and output flanges 106. Element 107 is the input
to the flow meter; element 108 is the output. Conduit 101 as an input end 109
connected to an opening in case end 104 at element 112 which is the brace bar portion
of case end 104. Brace bar portion 12 is coupled to neck element 105. On the right
side, the output end 110 of conduit 101 is coupled to the case end 104 at location 112
where case end 104 joins neck element 105.
In operation, conduit 0 1 and balance bar 02 are vibrated in phase opposition by
a driver (not shown). With a fluid flowing therein, the vibration of conduit 0 induces
a Coriolis response that is detected by pick-off sensors (not shown). The outputs of the
pickoff sensors are applied to electronics that processes the signals to derive the desired
infonnation pertaining to the flowing substance, such as for example a mass flow rate, a
density, a viscosity, etc. The phase displacement between the pick-off sensors
represents information pertaining to a mass flow rate of the fluid. A resonant frequency
at either pickoff sensor represents information pertaining to a density of the fluid.
The prior art single tube meter is kept in balance over a range of fluid densities
by way of a design that automatically adjusts the amplitude ratio between the flow
conduit and the balance bar. This has a significant drawback in that it results h the
repositioning of motionless nodes that reside along the axis of the vibrating structure.
Node relocation is a problem in flow meters because the nodes are typically located on
the conduit where the balance structure joins the conduit. Accordingly, the area
between the nodes usually defines the active length of the conduit. The active length
affects the measurement sensitivity. Further, if the nodes are repositioned, then the end
portions of the tube may vibrate. This further causes the flanges to vibrate. These
undesirable vibrations can further affect the measurement sensitivity.
In thermal compensation, the temperatures of different structural parts of the
meter can differ in their importance to the data output of the meter. The concept of
weighting the importance of a local temperature is key. If raising the temperature of the
case by 10 degrees (compared to the flow conduit temperature) results in a change in
indicated flow rate of 1%, and if raising the temperature of the balance structure 10
degrees results in a change in the indicated flow rate of 2%, then the balance structure
temperature is said to be twice as important as the case temperature in compensating for
thermal effects. The importance of the local temperature is proportional to its impact on
the indicated flow rate and density. This importance of local temperatures to a meter' s
performance can be determined either through experiment or, as is more commonly
done, through computer modeling.
In the past, temperature compensation has consisted of one temperature sensor on
the flow conduit to compensate for modulus shift with temperature. A temperature
sensor network comprising two or more standard temperature sensors on the balance
structure and/or case has been used to compensate for thermal stress. These standard
temperature sensors are usually RTDs and have a standard resistance, such as 100 ohms
at zero degrees C. The resistance of RTDs increases with temperature so that the
temperature of a RTD is determined from its resistance.
In a prior art thermal stress temperature compensation network, for instance, the
counterbalance temperature might be twice as important for generating the output data
as the case temperature. Such a meter would have two standard temperature sensors on
the counterbalance and one standard temperature sensor on the case. The sensors on the
counterbalance and case would be connected in series. Their resistances would thus be
added. Dividing the total resistance by three gives the average resistance and thus the
weighted average temperature. The result would be a temperature measurement that
weighted the balance structure temperature twice as heavily as the case temperature in
generating a weighted average temperature measurement for thermal stress
compensation.
The thermal stress compensation network is important in straight tube meters
where the change in temperature of non-tube components can put the flo conduit in
tension or compression and change its frequency and sensitivity to flow. In curved tube
meters, thermal stress is of less concern because the flow conduit can bend slightly to
accommodate the changing dimensions of other meter components. The result is that
curved tube meters show only very slight changes in frequency or sensitivity to flow due
to the tensioning effects of temperature change of the non-tube components.
Single curved tube meters have another problem. They use the same amplituderatio
balancing design as single straight tube meters. However, because the flow
conduit is much less stiff, the balance structure is also much less stiff and has a much
more active role in determining the vibration natural frequency. In other words, a
modulus shift in the balance structure can have as large an effect on the system
frequency as a modulus shift in the flow conduit Because the frequency is fundamental
in determining fluid density, and because density is necessary for compensating the f ow
output, it is necessary to compensate the output data for the temperature of the balance
structure.
The balance structure, in its deformation during drive vibration has areas of
relatively high stress and areas of relatively ow stress. The areas of high stress are
more important with respect to drive frequency than the areas of low stress. The
concept of importance is the same as for straight tube meters, except the straight tube
meter areas of importance change the frequency by putting the conduit in
tension/compression, whereas in single curved tube meters the areas of importance
change the frequency through modulus shift of the balance structure.
The prior art compensation method of using multiple standard temperature
sensors has drawbacks in either straight or curved tube meters. The required
temperature sensor network can become complex, requiring numerous temperature
sensors if the balance bar temperature importance is anything but an integer multiple of
the case temperature importance. For instance, the single conduit meter shown in FIG. 1
has a case temperature that is 3/8 as important as the balance structure temperature. The
prior art configuration of this network would be three temperature sensors located on the
case and eight temperature sensors located on the balance structure. All eleven
temperature sensors would be connected in series.
Such a solution is accompanied by drawbacks. Numerous temperature sensors
are required. This results in a high overall resistance. Further, a complex circuit and
numerous wires are needed. Materials costs are increased. Manufacturing costs are
increased. More resistive temperature sensors increase the likelihood of wiring faults
and operational failures, where one failure in a series circuit of multiple resistive devices
renders the circuit inoperative. More resistive temperature sensors will likely increase
the additive tolerance error.
Aspects of the Invention
In one aspect of tlie invention, a vibrating flow meter comprises:
a single curved flow conduit;
a conduit temperature sensor T \ affixed to tlie single curved flow conduit;
a balance structure affixed to and opposing the single curved flow conduit; and
a balance temperature sensor T affixed to tl e balance structure, wherein a
conduit temperature sensor resistance of the conduit temperature sensor
T and a balance structure temperature sensor resistance of the balance
temperature sensor T2 are selected to form a predetermined resistance
ratio.
Preferably, the predete ed resistance ratio corresponds to a temperature
importance ratio between tl e single curved flow conduit and the balance structure.
Preferably, the balance structure comprises a base coupled to the single curved
flow conduit and a driven structure extending from tlie base, with a first driver portion
of a vibratory driver being affixed to tlie driven structure and configured to interact with
a second driver portion affixed to the single curved flow conduit.
Preferabhy, tlie driven structure comprises a cantilevered arm that extends
generally orthogonally from the base.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the driven structure.
Preferably, tl e predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the base combined with the
driven structure.
Preferably, tlie conduit temperature sensor resistance and tlie balance structure
temperature sensor resistance are used to compensate a shift in elastic modulus with
temperature.of the single curved flow conduit.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a shift in elastic modulus with
temperature of the balance structure.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress with temperature
of the single curved flow conduit.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress with temperature
of the balance structure.
Preferably, the.balance temperature sensor T further comprises two or more
balance temperature sensors T and T affixed to one or more locations of the balance
structure and generate a balance structure temperature signal, wherein the two or more
balance structure temperature sensor resistances at the one or more balance structure
locations form a combined balance structure resistance related to thermal importances of
the one or more balance structure locations.
In one aspect of the invention, a method of measuring temperature in a vibrating
flow meter comprises:
measuring a conduit electrical current flowing through a conduit temperature
sensor T affixed to a single curved flow conduit of the vibrating flow
meter;
measuring a balance electrical current flowing through a balance temperature
sensor T affixed to a balance structure of the vibrating flow meter, with
the balance structure being affixed to and opposing the single curved flow
conduit; and
perforating one or more f ow meter temperature compensations using the
temperature measurement, wherein a conduit temperature sensor
resistance of the conduit temperature sensor T and a balance structure
temperature sensor resistance of the balance temperature sensor T2 are
selected to form a predetermined resistance ratio.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the balance structure.
Preferably, the balance structure comprises a base coupled to the single curved
flow conduit and a driven structure extending from the base, with a first driver portion
of a vibratory driver being affixed to the driven structure and configured to interact with
a second driver portion affixed to the single curved flow conduit.
Preferably, the driven structure comprises a cantilevered arm that extends
generally orthogonally from the base.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the driven structure.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between tlie single curved flow conduit and the base combined with the
driven structure.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a shift in elastic modulus with
temperature of the single curved flow conduit.
Preferably, tl e conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a shift in elastic modulus with
temperature of the balance structure.
Preferably, tlie co duit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress wit temperature
of the single curved flow conduit.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress with temperature
of the balance structure.
Preferably, the balance temperature sensor T further comprises two or more
balance temperature sensors T and T3 affixed to one or more locations of the balance
structure and generating a balance structure temperature signal, wherem tl e two or more
balance structure temperature sensor resistances at the one or more balance structure
locations form a combined balance structure resistance related to thermal importances of
tl e one or more balance structure locations.
In one aspect of tlie invention, a method of forming a vibrating flow meter
comprises:
foraiing a flow meter assembly including a single curved flow conduit and a
balance structure affixed to and opposing the single curved flow conduit;
affixing a conduit temperature sensor T to tlie single curved flow conduit; and
affixing a balance temperature sensor T2 to the balance structure, with a conduit
temperature sensor resistance of tlie conduit temperature sensor T and a
balance structure temperature sensor resistance of the balance temperature
sensor T being selected to form a predetermined resistance ratio.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the balance structure.
Preferably, the balance structure comprises a base coupled to the single curved
flow conduit and a driven structure extending from the base, with a first driver portion
of a vibratory driver being affixed to the driven structure and configured to interact with
a second driver portion affixed to the single curved flow conduit.
Preferably, the driven structure comprises a cantilevered arm that extends
generally orthogonally from t re base.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the driven structure.
Preferably, the predetermined resistance ratio corresponds to a temperature
importance ratio between the single curved flow conduit and the base combined with the
driven structure.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a shift in elastic modulus with
temperature of the single curved flow conduit.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a shift inelastic modulus with
temperature of the balance structure.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress with temperature
of the single curved flow conduit.
Preferably, the conduit temperature sensor resistance and the balance structure
temperature sensor resistance are used to compensate a thermal stress with temperature
of the balance structure.
Preferably, affixing the balance temperature sensor T further comprises affixing
two or more balance temperature sensors T and T3 to one or more locations of the
balance structure and generating a balance structure temperature signal, wherein the two
or more balance structure temperature sensor resistances at the one or more balance
structure locations form a combined balance structure resistance related to thermal
importances of the one or more balance structure locations.
Description of the Drawings
FIG. 1 depicts a single conduit type vibrating flow meter of the prior art.
FIG. 2 shows a vibrating flow meter according to the invention.
FIG. 3 shows the vibrating flow meter according to another embodiment of tl e
invention.
FIG. 4 shows the temperature sensors where the resistance ratio is about :2.
FIG. 5 shows the temperature sensors where the resistance ratio is about 1:5.
FIG. 6 shows a vibrating flow meter according to the invention.
FIG. 7 shows that the driven member and the flow conduit are preferably driven
about bending axis X, which is defined in part by the connectors.
FIG. 8 shows a flow conduit rotation that results in the base rocking slightly, in
phase with the driven member.
FIG. 9 shows a flow conduit rotation where the base rocks slightly, but in phase
with the conduit.
Detailed Description of the Invention
FIGS. 2-9 and the following description depict specific examples to teach those
skilled in tlie art how to make and use tlie best mode of the invention. For the purpose
of teaching inventive principles, some conventional aspects have been simplified or
omitted. Those skilled in the art will appreciate variations from these examples that fall
within the scope of the invention. Those skilled in the art will appreciate that the
features described below can be combined in various ways to form multiple variations
of the invention. As a result, l e invention is not limited to tl e specific examples
described below, but only by the claims and their equivalents.
FIG. 2 shows a vibrating flow meter 205 according to tl e invention. The
vibrating flow meter 205 comprises a Coriolis mass flow meter or a vibrating
densitometer. The vibrating flow meter 205 includes a flow conduit 210, a base 260
coupled to the flow conduit 210, and a driven member 250 that extends from the base
260 (see also FIGS. 6-9 and the accompanying discussion below). A dr ver 220 (see
FIG. 6 and the accompanying discussion) is formed of components affixed to the
conduit 201 and to tlie driven member 250. During operation of the vibrating flow
meter 205, the driver 220 vibrates the flow conduit 2 0 with respect to tlie driven
structure 250.The driver 220 will cause the driven member 250 to vibrate substantially
in opposition to the flow conduit 2 1Q. Consequently, when the flow conduit 210 is
moved in one direction, the driven member 2 will be moved substantially in the
opposite direction, counter-balancing the flow conduit 210. The flow conduit 2 0 may
vibrate with an amplitude and frequency that is the same as, or different from, the
vibrational characteristics of the balance structure 2 .
Although a curved flow conduit is shown, the temperature sensors are not limited
to curved conduit flow meters. Likewise, although a single flow conduit is shown, the
temperature sensors according to the invention are not limited to single conduit flow
meters or flow meters that employ a balance bar or oilier balance structure.
The vibrating flow meter 205 further includes a conduit temperature sensor T
2 and a balance temperature sensor T 292 configured for modulus compensation. In
some embodiments, the temperature sensors can comprise resistive temperature devices
(RTDs). The conduit temperature sensor 291 is affixed to the flow conduit 210 and
measures the flow conduit temperature. The conduit temperature sensor T 291
generates a flow conduit temperature signal. Although the conduit temperature sensor
291 is shown as being located near the driver location at the center of the f ow
conduit 2 0, it should be understood that the conduit temperature sensor T 291 can be
located anywhere on the flow conduit 210.
The balance temperature sensor T 292 is affixed to the balance structure 208 and
measures the balance structure temperature. The balance temperature sensor T 292 can
be affixed to the driven member 250 or can be affixed to the base 260, for example. The
balance temperature sensor T 292 generates a driven member temperature signal. It
should be understood that the balance temperature sensor T 292 can be located
anywhere on the bal nce structure 208.
In some embodiments, the balance temperature sensor T 292 is affixed to the
driven member 250, as the driven member 250 is most likely to be affected by modulus
changes with temperature. In some embodiments, the driven member 2 0 comprises a
cantilevered arm that extends generally orthogonally from the base 260. Alternatively,
the balance temperature sensor T 292 can be mounted to the base 260. However, the
location of the balance temperature sensor T 292 is not restricted to any particular
position, and could be located at any desired spot on the balance structure 208.
In the figure, the balance temperature sensor T 292 is represented as being
physically larger than the conduit temperature sensor T 291 . The difference in physical
proportions is done to show a possible difference between internal resistances of the
conduit temperature sensor 2 and the balance temperature sensor T 292 (the
resistances can be equal, however). The difference illustrates that the resistance of the
conduit temperature sensor 2 1 and the resistance of the balance temperature sensor
T 292 are chosen to provide a predeteraimed resistance ratio. The resistance ratio is set
according to the relative importance of local temperatures on the output data. This is
done where a conduit temperature response differs from a base temperature response,
e.g., where a change in temperature during operation of the vibrating flow meter 205
(with all other factors remaining unchanged) will result in a change in measurement
signals generated by one or both pick-off sensors 230 and 23 .
The vibrating flow meter 205 of some embodiments includes a predetermined
resistance ratio corresponding to a temperature importance ratio between the flow
conduit 2 and the balance structure 208. The vibrating flow meter 205 of some
embodiments includes a predetermined resistance ratio corresponding to a temperature
importance ratio between the flow conduit 210 and the driven structure 250. The
vibrating flow meter 205 of some embodiments includes a predetermined resistance
ratio corcesponding to a temperature importance ratio between the flow conduit 210 and
the base 260.
Alternatively, or in addition, a predetermined resistance ratio can be formed on
the driven structure 250 versus the base 260 of the balance structure 208. The driven
structure 250 may include the temperature sensor T 292 and the base 260 can include a
temperature sensor T3 293 (dashed lines). The temperature sensor T2 292 and the
temperature sensor T 293 may form a second resistance ratio, if desired, wherein the
thermal importance of the driven structure 250 versus the base 260 may be fully
characterized.
The temperature importance ratio can comprise a quantification of how a change
in temperature will affect the elastic modulus of that component. The temperature
importance ratio can quantify how a change in flow fluid temperature (or environmental
temperature) wil transfer into the component. For example, the base ends respond more
quickly to fluid temperature changes than the base center. Temperature sensors may
therefore be located at the ends and center of the base 260. These sensors may be
selected to have the proper resistance ratio to match their relative importance. The
resistance of the sensors on the base 260 can then be added to establish the desired
importance (and resistance) ratio with the flow conduit 2 10.
The temperature importance ratio can comprise an experimentally-derived value
in some embodiments. In other embodiments, the temperature importance ratio can be
determined from the known heat transfer properties of the flow meter materials and the
known quantities of these materials, such as through computer modeling. However, it
should be understood that the temperature importance ratio can be obtained in other
ways.
The temperature sensor resistance values can be set or formed in any suitable
manner. For example, a temperature sensor can be formed by trimming (such as laser
trimming or etching, for example), cutting or burning out elements of a resistor ladder,
welding or joining together resistive units, et cetera.
In some embodiments, where the total resistance R O is not a concern, the
temperature sensors 29 1 and 292 may be chosen in any manner. For example, one
temperature sensor can be chosen to be a standard resistance and a second temperature
sensor can be configured to obtain the predetermined resistance ratio. Alternatively, the
total resistance R OTcan first be chosen, and then one or both temperature sensors can
be configured to obtain the predetermined resistance ratio. This approach ensures that
the total resistance RT of the two temperature sensors of the temperature sensor
network is not too large or too small.
A method of measuring- temperature in a vibrating flow meter according to some
embodiments comprises measuring an electrical current flowing through a conduit
temperature sensor T affixed to a flow conduit of the vibrating flow meter and through
a balance temperature sensor T affixed to a balance structure of the vibrating flow
meter, with the electrical current comprising a temperature measurement, and
perforating one or more flow meter temperature compensations using the temperature
measurement. A conduit temperature sensor resistance of the conduit temperature
sensor T 2 and a balance structure temperature sensor resistance of the balance
temperature sensor T 292 are selected to form a predetermined resistance ratio.
A method of forming a vibrating flow meter according to some embodiments
comprises forming a flow meter assembly including a balance structure and a flow
conduit, affixing a conduit temperature sensor 291 to the flow conduit, and affixing a
balance temperature sensor T 292 to the balance structure. A conduit temperature
sensor resistance of the conduit temperature sensor 2 1 and a balance structure
temperature sensor resistance of the balance temperature sensor T 292 are selected to
form a predetermined resistance ratio.
In some embodiments, one or more additional balance structure temperature
sensors, such as temperature sensors T2 292 and T 293 in FIG. 2, may be included in
order to fully characterize the balance structure 208. As an example, where the base
temperature is twice as important as the driven structure temperature, then twice as
many temperature sensor elements can be affixed to the base 260 of the balance
structure 208 versus the driven structure 250. As a consequence, a temperature change
in the base 260 will have twice the effect on sensor electrical resistance as a temperature
change in the driven structure 250. The resistance change of the three temperature
sensors in series may then be divided by thi ee to give the weighted average temperature
of the balance structure 208. Multiple temperature sensors can also be put in parallel, or
in other electrical network configurations, n order to characterize the thermal
importance of regions of the balance structure 208.
The temperature sensors according to the invention provide several benefits. The
temperature sensors according to the invention require only two sensor elements for the
vibrating flow meter 205. The temperature sensors according to the invention require
only two wires. The need for fewer resistive elements means fewer opportunities for
tolerance errors. The need for fewer resistive elements means a smaller statistical
likelihood of having additive tolerance problems.
The temperature sensors according to the invention provide electrical resistances
in proportion to the thermal importance of the components. Consequently, temperature
compensation is more easily achieved and is more accurate and representative.
The invention addresses the problem of unequal thermal effects by employing
temperature sensors having resistances according to a predetermined resistance ratio.
This can include using custom-made temperature sensors, wherein the ratio of the base
resistance (i.e., the resistance at 0 degrees C) of the conduit temperature sensor Tj 291 to
the base resistance of the balance temperature sensor T 292 can be equal to the ratio of
the importance of the flow conduit and balance structure temperatures.
For instance, a standard temperature sensor has a resistance of 1 0 ohms. If this
temperature sensor was used to measure the balance structure temperature, a
temperature sensor with a base resistance of 37.5 ohms could be used to measure the
flow conduit temperature, with the resistance ratio being 37.5 ohms to 100 ohms, or a
resistance ratio of about 3:8. But, in contrast to the prior art, only two temperature
sensors are needed, and not eleven temperature sensors. If the two temperature sensors
are made of the same material, having essentially the same temperature coefficient, then
when connected in series, they will give the desired result. Subsequently, the change in
resistance due to the sensed combined temperature will accurately predict the change in
mass flow rate and/or vibrational frequency with the change in temperature.
FIG. 3 shows the vibrating flow meter 205 according to another embodiment of
the invention. The improvement in temperature measurement can be used for
compensating the flow meter for thermal stress, as in straight tube meters. In this
embodiment, the conduit temperature sensor T 291 comprises a first temperature
measuring circuit and the balance temperature sensors T2 292 and T3 293 comprise an
independent second temperature measuring circuit As a result, the meter electronics 26
receives separate flow conduit and balance structure temperature measurements. This
embodiment may be employed where thermal stress is significant, such as in straight or
slightly curved flow conduits, for example. Thermal stress is caused by a difference in
temperature between the flow conduit and other parts of the meter, as when hot fluid
flows through a meter in a cold environment. Thermal stress compensation requires that
two temperatures be known: that of the flow conduit and that of the weighted average of
other meter components. The flow conduit temperature is used separately from the
weighted average in some embodiments of modulus compensation of the flow tube. In
addition, the difference between the flow conduit temperature and the weighted average
temperature can then also be determined.
The improvement in temperature measurement can be used with curved tube
meters for compensating the flow meter for modulus shift. The temperatures of regions
of importance of the vibrating system of the flow conduit and the balance structure are
measured such that the weighted average temperature is used to determine and
compensate for the modulus shift of the vibrating structure.
Because it is highly unlikely that the temperature importance ratio is exactly twoto-
one, or any other integer ratio, the accuracy of the stress compensation may be
improved by matching the exact ratio with the resistance ratio.
In some embodiments, the tliermal stress compensation equation comprises:
FCF = Kl * T ib + K2 * (T - Ta g) (1)
where T i is the weighted average temperature of the vibrating system and Ta is
the weighted average of the thermal stress components. In curved tube meters, 2 may
be small enough to render the second term insignificant.
Given a linear relationship between the temperature difference and the error in
the tube period squared (due to thermal stress), it is a simple matter to determine the
proportionality constants (Kl and K2) through thermal calibration. Alternatively, the
weighted average temperature T may be replaced (or augmented) by a balance
structure temperature measurement. Thereafter, the meter can be compensated for
thermally-generated error.
The First compensation term (Kl *T ) may perform elastic modulus
compensation of the vibrating structure. The second compensation term (K2*(Tto -
Ta g)) may perform thermal stress compensation.
Generally, if the flow conduit 2 10 and the balance structure 208 are of the same
material, then thermal stress generally only occurs with a difference in temperature
between the flow conduit temperature and the balance structure average temperature.
All Coriolis flow meters require compensation to correct the signals that are
generated by the Coriolis force-induced displacement of the vibzating flow tube. These
signals represent the phase difference between the spaced-apart flow tube pickoffs and
are indicative of the material flow through the flow meter. Curved and straight tube
meters both need compensation for the change in elastic modulus of the flow tube with
temperature. As the flow tube and balance structure temperatures rise, the modulus
decreases and the meter becomes more sensitive. Compensation for the change in the
elastic modulus is achieved by use of temperature sensors on the vibrating structure and
the use of the temperature measurements in an appropriate compensation algorithm in
the meter electronics.
The density is derived from the resonant frequency of tlie flow conduit plus any
fluid within tlie conduit, whether flowing or non-flowing. The density is determined as:
Here, the (b) terai is a calibration factor that is usually determined during a
calibration operation, while the (f) term is the frequency of the vibrational response of
the flow meter. The K term represents the stiffness of tl e meter and includes the elastic
modulus of the meter material. Clearly, changes in the elastic modulus due to
temperature will also affect density measurements.
FIG. 4 shows the temperature sensors 291 and 292 where the resistance ratio is
about :2. For example, the conduit temperature sensor T 2 can have an electrical
resistance of about 100 ohms, while the balance temperature sensor T 292 can have a
resistance of about 200 ohms. This is one example, and other resistance values can be
employed. Consequently, tlie balance temperature sensor T 292 has a resistance of
about two times the resistance of the conduit temperature sensor 291.
Again, the two temperature sensors are shown in physical sizes that graphically
represent their relative electrical resistance s. However, it should be understood that tl e
two temperature sensors may be of any size, and their physical proportions do not
necessarily control or affect their resistance levels.
FIG. 5 shows the temperature sensors 29 and 292 where the resistance ratio is
about 1:5. For example, the conduit temperature sensor T 291 can have an electrical
resistance of about 0 ohms, while the balance temperature sensor T 292 can have a
resistance of about 500 ohms. Tins is one example, and other resistance values can be
employed. Consequently, the balance temperature sensor T 292 has a resistance of
about five times the resistance of the conduit temperature sensor T 291.
FIG. 6 shows a vibrating flow meter 205 according to the invention. FIGS. 6-9
illustrate examples of a vibrating flow meter 205 in the form of a Coriolis flow meter,
comprising a sensor assembly 206 and a balance structure 208. The one or more meter
electronics 26 are connected to sensor assembly 206 via leads 1 0, 1 1 1, 111' to measure
a characteristic of a flowing substance, such as, for example, density, mass flow rate,
volume flow rate, totalized mass fl ow temperature, and other information. The meter
electronics 26 can transmit the information to a user or other processor.
The sensor assembly 206 includes a conduit 210 that defines a flow path for
receiving a flowing substance. The conduit 210 may be bent, as shown, or may be
provided with any other shape, such as a straight configuration or an irregular
configuration. When sensor assembly 206 is inserted into a pipeline system which
carries the flowing substance, the substance enters sensor assembly 206 tlirough an inlet
flange (not shown), then it flows tlirough the conduit 210, where a characteristic of the
flowing substance is measured. Following this, the flowing substance exits the conduit
210 and passes tlirough an outlet flange (not shown). Those of ordinary skill in the art
appreciate that the conduit 210 can be connected to the flanges, such as flanges 106,
shown in FIG. 1, via a variety of suitable means. In the present embodiment, the
conduit 210 is provided with end portions 2 1 , 212 that extend generally from
connectors 270, 271 and connect to the flanges at their outer extremities.
The sensor assembly 206 of the present example includes at least one driver 220.
The driver 220 includes a first portion 220A connected to a driven member 250 of the
balance structure 208 and a second portion 220B comiected to the conduit 210. The first
and second portions 220A, 220B may correspond to a drive coil 220A and a drive
magnet 220B, for example. In the present embodiment, the driver 220 preferably drives
the driven member 250 and conduit 210 in phase opposition.
FIG. 7 shows mat the driven member 250 and conduit 210 are preferably driven
about bending axis X, which is defined in part by the connectors 270, 271 . According to
an embodiment of the invention, the bending axis X corresponds to the inlet-outlet tube
axis. The driven member 250 bends from the base 0. The driver 220 may comprise
one of many well known arrangements, including for example, and not limitation
piezoelectric elements or an electromagnetic coil/magnet arrangement.
As s o in FIG. 6, the sensor assembly 206 includes at least one pick-off. The
embodiment shown is provided with a pair of pick-offs 230, 231. According to one
aspect of the present embodiment, the pick-offs 230, 23 1 measure the motion of the
conduit 210. In the present embodiment, the pick-offs 230, 2 include a first portion
located on respective pick-off arms 280, 281 and a second portion located on the conduit
210. The pick-off(s) may comprise one of many well known arrangements, including
for example, and not limitation piezoelectric elements, capacitance elements, or an
electromagnetic coil/magnet arrangement. Therefore, like the driver 220, the first
portion of the pick-off may comprise a pick-off coil while the second portion of the
pick-off may comprise a pick-off magnet. Those of ordinary skill in the ai will
appreciate that the motion of the conduit 2 0 is related to certain characteristics of the
flowing substance, for example, the mass flow rate or density of the flowing substance
through the conduit 10.
Those of ordinary skill in the art will appreciate that the one or more meter
electronics 26 receives the pick-off signals from the pick-offs 230, 2 and provides a
drive signal to the driver 220. The one or more meter electronics 26 can measure a
characteristic of a flowing substance, such as, for example, density, mass flow rate,
volume flow rate, totalized mass flow, temperature, and other information. The one or
more electronics 207 may also receive one or more other signals from, for example, one
or more temperature sensors (not shown), and one or more pressure sensors (not shown),
and use this information to measure a characteristic of a flowing substance. Those of
ordinary skill in the art will appreciate that the number and type of sensors will depend
on the particular measured characteristic.
FIGS. 6-9also depict the balance structure 208 of the present embodiment.
According to one aspect of the present embodiment, the balance structure 208 is
configured to at least partially balance the vibrations of the conduit 210. According to
one aspect of the present embodiment, the balance structure 208 is configured to at least
partially balance the momentum of the conduit 210.
As shown in FIGS. 6-9, the balance structure 208 includes a base 260 connected
to the driven member 250. As shown, the driven member 250 is preferably a
cantilevered arm that extends generally orthogonal from the base 260. The base 260 n
the present embodiment is preferably relatively massive and immobile as compared to
the driven member 250. For example, and not limitation, the base 260 may be provided
with a mass at least 5 times greater than that of the driven member 250. For example
and not limitation, the base 260 may be provided with a mass at least 5 times greater
than the mass of the conduit 210. In some embodiments, these numbers may be greater,
for example 14 and 8 times greater than the driven member 250 and the conduit 210,
respectively.
The balance structure 208 in the present embodiment is coupled to the conduit
210. As shown, the base 260 includes a pair of connectors 270, 271, which may be in
the form of the plates shown or which may be provided with a other shape. In the
present embodiment, the connectors 270. 271 couple the base 260 to an interior of the
end portions 2 , 212 of the conduit 2 1 . In the embodiment shown, the pair of
connectors 270, 271 are coupled to opposing end faces 261, 62 of the base 260 to the
respective end portions 2 1, 212 of the conduit 210.
According to one aspect of the present embodiment, the conduit 210, the driven
member 250, and the base 260 are configured to provide a balanced system. It should
be appreciated tha the system may not be absolutely balanced. However, the system is
designed to be more balanced than prior art systems that do not include the balance
structure 208. In the present embodiment, the conduit 2 0 and the driven member 250
act as two separate vibrating systems, which are driven at equal resonant frequencies, in
phase opposition about axis X. As shown in FIG. 7, the driven member 250 vibrates at
its resonant frequency by flexing upon the base 260. Those of ordinary skill in the art
will appreciate that FIG. 7 represents an exaggeration of the motions involved, in order
to better convey the concepts of the present embodiment. Also shown in FIG. 7, the
conduit 210 vibrates out of phase with the driven member 250.
The motion of the conduit 2 0 about axis X applies torque to the connectors 270,
271. Those of ordinary skill in the art will also appreciate that the motion of the driven
member 250 about the axis X also applies torque to the connectors 270, 271, via the
base 260. Assuming, for the sake of simplicity, that the mass of the conduit 210,
including the mass of the flowing substance, and the mass of the driven member 250 are
equal, then the driven member 250 and conduit 210 may be driven in phase opposition,
at equal frequency, and with equal amplitude to provide a balanced system.
In this example, the momentum of both the conduit 210 and the driven member
250 are balanced, since momentum is the product of mass and velocity and velocity is
proportional to vibration amplitude. The result being that the torques applied to the
connectors 270, 271 are nearly equal and of opposite sign, thus canceling out. Further,
motionless nodes are located substantially along the end portion 2 , 212 axes and
substantially where the connectors 270, 271 connect to the conduit 210. Accordingly,
an overall balanced system is provided and torque and vibrations substantially cancel
out. Furthermore, little or no torque is applied to the outer extremities of the end.
portions 2 11, 212 of the conduit 210 and to the flanges.
According to one aspect of the present embodiment, the conduit 210 and balance
structure 208 are preferably isolated from any connecting structures by relatively soft
mounts, which are designed to limit the translation of motion to any connecting
structures. Accordingly, the conduit 210 and balance structure 208 function as an
isolated vibrating structure with two masses vibrating in phase opposition at tl e same
frequency, which self balances. Accordingly, there are two vibrating systems, i.e. a
vibrating conduit system, which may include the conduit 210 or the conduit 210, as well
as the connectors 270, 271 and the base 260, and the vibrating driven member system,
which may include the driven member 250 or the driven member 250, as well as the
connectors 270, 271 and base 260, as hereinafter discussed. The two vibrating systems
are separated by common motionless nodes that preferably substantially lie upon the
axis of end portions 2 11, 2 2 of the conduit 210, substantially proximate to the
connectors 270, 271 .
Advantageously, the present arrangement may also provide numerous advantages
when the mass of the conduit 2 changes. For example, the mass of the conduit 2 0
may increase, such as, for example, when the mass of the flowing substance within the
conduit 210 increases or the mass of the conduit 210 itself increases due to, for example,
a coating buildup. When this occurs, the vibration frequency and the vibration
amplitude of the conduit 210 decrease. This occurs automatically as a result of the
additional mass and the soft mounting of the combined vibrating structure. Further, as a
natural response, the vibration amplitude of the driven member 250 increases. This
change in amplitude ratio causes node relocation. However, the nodes merely move
inward along the conduit axis X in a region where the conduit's motion is purely
rotational about its own axis. The pure rotation may be ensured using the case connects
590, 591. Because no Coriolis force is generated by pure rotation of tire conduit about
its own axis X, the motion of the nodes along the axis X does not affect the output
signal.
FIG. 8 shows a flow conduit rotation that results in the base 260 rocking slightly,
in phase with the driven member 250.1n the present embodiment, the increase in the
vibration amplitude of the driven member 250 is reflected as an increase in the range of
motion about which the driven member 250 flexes about the base 260. This motion
increase is slight, but nevertheless results in additional torque being applied to the base
260 which is further translated as torque to the connectors 270, 271. This additional
torque causes the connectors 270, 271 and the base 260 to rotate very slightly, about the
axis of the en portions 2 , 2 2 of the conduit 1 in phase with the driven member
250. Although exaggerated in the figures for illustrative purposes, those of ordinary
skill in the art will appreciate that the rocking motion of the base is slight because of the
mass of the base 260 and the flexibility of the driven member 250.
Accordingly, the base 260 and connectors 270, 271 rotate about an axis X
extending through the end portions , 12, in phase with the driven member 250,
forming a vibrating system. Whereas the frequency of the conduit 210 decreases due to
the initial increase of mass, the coupling of the motion of the driven member 250 with
the base 260 and connectors 270, 27 has the same effect; an increase in mass and a
decrease in frequency. Thus, the frequency of the driven member 250 is lowered to
substantially match the frequency of the conduit 210. Similarly, the coupling of the
mass of the base 260 and the connectors 270, 2 1 increases the amplitude of the driven
member 250. such that the momentum of the driven member 250 aid base 260 equals
the momentum of the flow tube 210, and thus balance is restored.
Similarly, the mass of the conduit 210 may decrease, such as, for example, when
the mass of the flowing substance within the conduit 210 decreases. When this occurs,
the vibration frequency and the vibration amplitude of the conduit 210 increase. This
occurs automatically as a result of the reduction in mass. Further, as a natural response,
the vibration amplitude of the driven member 250 decreases. Again, this change in
amplitude ratio results in node relocation along the inlet-outlet tube axis X with
substantially no impact on the meter output.
FIG. 9 shows a flow conduit rotation where the base 260 rocks slightly, but in
phase with the conduit 210. In the present embodiment, the increase in the vibration
amplitude of the conduit 210 is reflected as an increase in the range of motion about
which the conduit 210 flexes about the axis X of end portions 10, 2 1. This motion
increase is again slight, but nevertheless results in additional torque being applied to the
connectors 270, 271, which is further translated as torque to the base 260. This
additional torque causes the connectors 270, 271 and the base 260 to rotate veiy slightly,
about the axis X of the end portions 2 , 212 of the conduit . This rotation results in
the base 260 rocking slightly, but in phase with the conduit 210. Although exaggerated
in the figures for illustrative purposes, those of ordinary skill in the ait will appreciate
that the rocking motion of the base 260 is slight because of the mass of the base 260 and
the flexibility of the conduit 21 .
Accordingly, the base 260 and connectors 270, 271 rotate about an axis X
extending through the end portions 2 1 , 212, in phase with the conduit 210, forming a
vibrating system. ereas the frequency of the conduit 210 is increased due to the
lowering of fluid mass, the coupling of the mass of the base 260 and connectors 270,
271 has the opposite effect, lowering the frequency. The net effect is that the frequency
is raised slightly. Similarly, the rotation of the mass of the base 260 and the connectors
270, 271 with the flow conduit 210 reduces the amplitude of the driven member 250,
and slightly increases its frequency to equal that of the flow conduit 210. Thus, the
amplitude ratio of the conduit 210 and the driven member 250 is changed such that the
momentum of the driven member 250 and the base 260 is substantially equal to the
momentum of the flow conduit 210, and thus, balance is restored.
As the base 260 is preferably provided with a relatively large mass, o y a very
slight change in the vibration amplitude of the base 260 is required to cause a relatively
large change in the vibration characteristics of the conduit 210 and driven member 250.
The base 260 slightly rotates with and adds its mass to the flow conduit 210 when a low
density fluid is flowing. It slightly rotates with and adds its mass to the driven member
250 when a high density fluid is flowing. It thus adds its mass to the light member (the
flow conduit 210 or the driven member 250). Balance is further maintained by the
changing of vibration amplitude such tha the light member increases its vibration
amplitude while the heavier member decreases its vibration amplitude. Furthennore, the
small vibration amplitude of the base 260 imparts only a small torque applied to the
inner ends of the end portions 11, 212 of the conduit 210. Accordingly, only a very
slight amount of torque is applied to the case 300 with fluids of high or low density.
Accordingly, in the present embodiment, the base 260 switches between moving
in phase with the conduit 2 0 and moving in phase with the driven member 250
according to the mass of the flow conduit 2 10 and more particularly, to the density of
the flowing substance. Preferably, the base 260 and the inner ends of the end portions
11, 212 are motionless with flowing substances having a specific gravity of
approximately 1000 kg/nr . Preferably, with substances having a specific gravity less
than approximately 1000 kg/ , the conduit 210 has higher amplitude, the driven
member 250 has lower amplitude, and the base 260 and connectors 270, 271 rotate very
slightly with the conduit 210. The conduit end portions 2 1 , 212, would also rotate very
slightly with the conduit 10. Preferably, with substances having a specific gravity of
greater than approximately 1000 kg/mJ, the conduit 210 has lower amplitude, the driven
member 250 has higher amplitude, and the base 260 and connectors 270, 271 rotate very
slightly with the driven member 250. In this case, the conduit end portions 2 1, 212
would also rotate very slightly with the base 260 and connectors 270, 271 . Since pure
rotation of the conduit 210 about its own axis in end portions 11, 212 does not impart
Coriolis acceleration to the flowing substance, meter sensitivity will therefore be largely
unaffected. It should be appreciated that the particular fluid densities illustrated above
are merely examples and the particular fluid density may vary. According to another
embodiment of the invention, the size and stiffness of the balance structure 208 may be
chosen such that the base 260 is substantially motionless when there is no fluid within
the conduit 2 0 (an added density of zero). In this case, the base 260 would rotate
slightly, flowing with the driven member 250 whatever the fluid density. In yet another
embodiment, the size and stiffness of the balance structure 208 may be chosen such that
the base 260 rotates with the conduit 210 for all expected fluid density ranges. In other
words, some maximum fluid density could be selected where the flow meter is expected
to operate with fluids under the maximum fluid density. Therefore, during substantially
all expected operating conditions, the fluid density would be under the maximum fluid
density resulting in the base 260 rotating with the conduit 210 substantially all of the
time. The amplitude of the rotation of the base would, however, vary with the density of
the fluid. It should be appreciated that should the fluid density exceed the maximum
fluid density, the base 260 would then rotate with the driven member 250 as described
above. Likewise, with a fluid density at the maximum fluid density, the base 260 would
remain substantially stationary.
It should also be appreciated that while the majority of the description discusses
the base 260 moving in response to a change in fluid density, it should be appreciated
that other conditions may occur that would change tire mass of the conduit 210, such as
for example, corrosion, erosion, deposition, etc. Therefore, the base 260 can
compensate for a variety of conditions that may change the flow conduit mass.
In the present embodiment, the end portions 2 11, 2 are preferably long
enough, for example, and not limitation, preferably at least three tube diameters long,
such that they are substantially soft in torsion. This further reduces the torque applied to
the flanges and outer extremities of the end portions 2 11, .
As shown in FIG.6, the sensor assembly 206 may also include a case 0 and
case connects 590, 591. The case connects 590, 591 shown include a first portion 595
connected to the conduit 210 and a second portion 596 connected to the case 300. As
shown, the case connects 590, 591 are preferably the only structures supporting the
conduit located between the flanges and the connectors 270, 271.
According to one aspect of the present embodiment, the case connects 590, 591
are preferably configured to provide support for the vibrating system that is rigid in
axial and transverse translation yet soft in torsion. This may be accomplished by
providing the case connects 590, 591 with defonnable members 592, 593, 594, for
example, which extend radially with respect to the axis of the end portions 2 11, 212 of
the conduit 0. Although three defonnable members 592, 593, 594 are provided, it
should be appreciated that any number of deformable members 592, 593, 594 may be
used and the particular number of deformable members should not limit the scope of the
present invention. They may be mounted to the conduit 210 in any manner, including,
for example a central hub 595 connected to the conduit 210. The rigid translational and
soft torsional coupling provides at least two functions. First, by limiting the end
portions 2 1, 212 to torsional movement, they constrain the nodes to the end portion
axis and thus limit measurement errors associated with node relocations. Secondly, by
allowing the end portions freedom to rotate, the vibrating structure is supported -
torsionally in a very soft manner. The soft mount enables the amplitude ratio to change
with fluid density and enables the self-balancing feature of this invention.
Although the present invention has been described in terms of resistive
temperature sensors, those skilled in the art recognize that any type of resistive sensor
could be used in place of a temperature sensor. For example, one might use a strain
gauge which indicates strain in the fo n of a variable resistance in place of one or more
of the temperature sensors described herein. The present invention can be applied using
any sensor that indicates a condition by changing its resistance. The essence of the
present invention applies equally to any such a configuration.
The vibrating flow meter according to the invention can be employed according
to any of the embodiments in order to provide several advantages, if desired. The meter
according to the invention provides a thermal elasticity-compensated curved tube meter.
The meter according to the. invention provides a thermal stress compensated curved tube
meter.
The detailed descriptions of the above embodiments are not exhaustive
descriptions of all embodiments contemplated by the inventors to be within the scope of
the invention. Indeed, persons skilled in the art will recognize that certain elements of
the above-described embodiments may variously be combined or eliminated to create
further embodiments, and such further embodiments fall within the scope and teachings
of the invention. It wi l also be apparent to those of ordinary skill in the art that the
above-described embodiments may be combined in whole or in part to create additional
embodiments within the scope and teachings of the invention. Accordingly, the scope
of the invention should be determined from the following claims.
What is claimed is:
1. A vibrating l ow meter (205), comprising:
a single curved flow conduit ( );
a conduit temperature sensor T (291) affixed to the single curved flow conduit
(2 0)
a balance structure (208) affixed to and opposing the single curved flow conduit
(210); an
a balance temperature sensor T (292) affixed to the balance structure (208),
wherein a conduit temperature sensor resistance of the conduit
temperature sensor T (291) and a balance structure temperature sensor
resistance of the balance temperature sensor T2 (292) are selected to form
a predetermined resistance ratio.
2. The vibrating flow meter (205) of claim 1, with the predetermined resistance
ratio corresponding to a temperature impoitance ratio between the single curved flow
conduit (210) and the balance structure (208).
3. The vibrating flow meter (205) of claim 1, with the balance structure (208)
comprising:
a base (260) coupled to the single curved flow conduit (2 0); and
a driven structure (250) extending from the base (260), with a first driver portion
(220A) of a vibratory driver (220) being affixed to the driven structure
(250) and configured to interact with a second driver portion (220B)
affixed to the single curved flow conduit (210).
4. The vibrating f ow meter (205) of claim 3 with the driven structure (250)
comprising a caritilevered arm that extends generally orthogonally from the base (260).
5. The vibrating flow meter (205) of claim 3, with the predetermined resistance
ratio corresponding to a temperature importance ratio between the single curved flow
conduit ( ) and the driven structure (250).
6. The vibrating flow meter (205) of claim 3 with the predetermined resistance
ratio corresponding to a temperatuie importance ratio between the single curved flow
conduit (210) and the base (260) combined with the driven structure (250).
7. The vibrating flow meter (205) of claim , with the conduit temperature sensor
resistance and the balance structure temperature sensor resistance being used to
compensate a shift in elastic modulus with temperature of the single curved flow conduit
(210).
8. The vibrating flow meter (205) of claim , with the conduit temperature sensor
resistance and the balance structure temperature sensor resistance being used to
compensate a shift in elastic modulus with temperature of the balance structure (208).
9. The vibrating flow meter (205) of claim 1, with the conduit temperature sensor
resistance and the balance structure temperature sensor resistance being used to
compensate a thermal stress with temperature of the single curved flow conduit (210).
10. The vibrating flow meter (205) of claim 1, with the conduit temperatui e sensor
resistance and the balance structure temperature sensor resistance being used to
compensate a thermal stress with temperature of the balance structure (208).
11. The vibrating flow meter (205) of claim 1, with the balance temperature sensor
T (292) further comprising two or more balance temperature sensors T (292) and T3
(293) affixed to one or more locations of the balance structure (208) and generating a
balance structure temperature signal, wherein the two or more balance structure
temperature sensor resistances at the one or more balance structure locations form a
combined balance structure resistance related to thermal importances of the one or more
balance structure locations.
12. A method of measuring temperature in a vibrating flow meter, the method
comprising:
measuring a conduit electrical current flowing through a conduit temperature
sensor affixed to a single curved flow conduit of the vibrating flow
meter;
measuring a balance electrical current flowing through a balance temperature
sensor T affixed to a balance structure of the vibrating flow meter, with
the balance structure being affixed to and opposing the single curved flow
conduit; and
performing one or more flow meter temperature compensations using the
temperature measurement, wherein a conduit temperature sensor
resistance of the conduit temperature sensor and a balance structure
temperature sensor resistance of the balance temperature sensor T2 are
selected to form a predetermined resistance ratio.
13. The method of claim 12, with the predetermined resistance ratio correspondhig to
a temperature importance ratio between the single curved flow conduit and the balance
structure.
14. The method of claim 12. with the balance structure comprising:
a base coupled to the single curved flow conduit; and
a driven structure extending from the base, with a first driver portion of a
vibratory driver being affixed to the driven structure and configured to
interact with a second driver portion affixed to the single curved flow
conduit.
15. The method of claim 14, with the driven structure comprising a cantilevered arm
that extends generally orthogonally from the base.
6. The method of claim 14, with the predetermined resistance ratio corresponding to
a temperature importance ratio between the single curved flow conduit and the driven
structure.
17, The method of claim 14, with the predetermined resistance ratio corresponding to
a temperature importance ratio between the single curved flow conduit and the base
combined with the driven structure.
. The method of claim 12, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a shift in
elastic modulus with temperature of the single curved flow conduit.
. The method of claim 12, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a shift in
elastic modulus with temperature of the balance structure.
20. The method of claim , with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a thermal
stress with temperature of the single curved flow conduit.
2 . The method of claim 12, with the conduit temperature sensor resistance and the
balance stmcture temperature sensor resistance being used to compensate a thermal
stress with temperature of the balance stmcture.
22. The method of claim 12, with the balance temperature sensor T2 further
comprising two or more balance temperature sensors T and T affixed to one or more
locations of the balance structure and generating a balance structure temperature signal,
wherein the two or more balance structure temperature sensor resistances at the one or
more balance stmcture locations fonn a combined balance structure resistance related to
thermal importances of the one or more balance structure locations.
23. A method of forming a vibrating flow meter, the method comprising:
forming a flow meter assembly including a single curved flow conduit and a
balance stmcture affixed to and opposing the single curved flow conduit;
affixing a conduit temperature sensor to the single curved flow conduit; and
affixing a balance temperature sensor T to the balance structure, with a conduit
temperature sensor resistance of the conduit temperatuie sensor T and a
balance structure temperature sensor resistance of the balance temperature
sensor T being selected to form a predetermined resistance ratio.
24. The method of claim 23, with the predetermined resistance ratio corresponding to
a temperature importance ratio between the single curved flow conduit and the balance
structure.
25. The method of claim 23, with the balance structure comprising:
a base coupled to the single curved flow conduit; and
a driven structure extending from the base, with a first driver portion of a
vibratory driver being affixed to the driven structure and configured to
interact with a second driver portion affixed to the single curved flow
conduit.
26. The method of claim 25, with the driven structure comprising a cantilevered arm
that extends generally orthogonally from the base.
27. The method of claim 25, with the predetermined resistance ratio corresponding to
a temperatui e importance ratio between the single curved flow conduit and the driven
structure.
28. The method of claim 25, with the predetermined resistance ratio corresponding to
a temperature importance ratio between the single curved flow conduit and the base
combined with the driven structure.
29. The method of claim 23, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a shift in
elastic modulus with temperature of the single curved flow conduit.
30. The method of claim 23, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a shift in
elastic modulus with temperature of the balance structure.
31. The method of claim 23, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a thermal
stress with temperature of the single curved flow conduit.
32. The method of claim 23, with the conduit temperature sensor resistance and the
balance structure temperature sensor resistance being used to compensate a thermal
stress with temperature of the balance structure.
33. The method of claim 23, with affixing the balance temperature sensor T further
comprising affixing two or more balance temperature sensors T and T to one or more
locations of the balance structure and generating a balance structure temperature signal,
wherein the two or more balance structure temperature sensor resistances at the one or
more balance structure locations fo n a combined balance structure resistance related to
thermal importances of the one or more balance structure locations.