HK1234821B - Apparatus for determining a differential zero offset in a vibrating flowmeter and related method - Google Patents

Description

Apparatus and associated method for determining differential zero offset in a vibrating flow meter

Technical Field

The present invention relates to flow meters, and more particularly to methods and apparatus for determining changes in zero offset of a vibrating flow meter.

Background Art

Vibration sensors, such as vibrating densitometers and Coriolis flowmeters, are generally known and are used to measure the mass flow rate and other information of materials flowing through pipes within the flowmeter. Exemplary Coriolis flowmeters are disclosed in U.S. Patents 4,109,524, 4,491,025, and Reference (Re.) 31,450 (all to J.E. Smith et al.). These flowmeters have one or more pipes in straight or curved configurations. Each pipe structure in a Coriolis mass flowmeter has a set of natural vibration modes, which may be simple bending, torsional, or coupled. Each pipe can be driven to oscillate in a preferred mode.

Material flowing into the flow meter from a connected line on the inlet side of the flow meter is directed through one or more pipes and exits the flow meter through the outlet side of the flow meter. The natural vibration modes of the vibrating system are defined in part by the combined mass of the pipes and the material flowing within them.

When there is no flow through the flowmeter, the driving force applied to the pipe(s) causes all points along the pipe(s) to oscillate with the same phase or a small "zero offset" (which is the time delay measured at zero flow). When material begins to flow through the flowmeter, the Coriolis force causes each point along the pipe(s) to have a different phase. For example, the phase at the inlet end of the flowmeter lags the phase at the centralized driver location, while the phase at the outlet leads the phase at the centralized driver location. Pickups on the pipe(s) generate sinusoidal signals representing the motion of the pipe(s). The signals output from the pickoffs are processed to determine the time delay between the pickoffs. The time delay between two or more pickoffs is proportional to the mass flow rate of the material flowing through the pipe(s).

Meter electronics, connected to the driver, generate a drive signal to operate the driver and determine the mass flow rate and other properties of the material based on the signal received from the sensor. The driver can include one of many known arrangements; however, a magnet and opposing drive coil have been used with great success in the flow meter industry. An alternating current is delivered to the drive coil to vibrate the conduit(s) at the desired flow tube amplitude and frequency. It is also known in the art to provide the sensor as a magnet and coil arrangement very similar to the driver arrangement. However, when the driver receives a current that induces motion, the sensor can use the motion provided by the driver to induce a voltage. The time delay measured by the sensor is of very small magnitude, often measured in nanoseconds. Therefore, it is necessary to make the transducer output very accurate.

Typically, a Coriolis flowmeter can be initially calibrated and a flow calibration factor can be generated along with a zero offset. In use, the flow calibration factor can be multiplied by the time delay measured by the sensing element minus the zero offset to generate the mass flow rate. In most cases, the flowmeter is initially calibrated by the manufacturer and it is assumed that the flowmeter provides accurate measurements without requiring subsequent calibration. Furthermore, prior art methods involve user zeroing—calibrating the flowmeter after installation by stopping flow, closing valves, and thereby providing the meter with a zero flow reference under process conditions.

As mentioned above, many vibration sensors (including Coriolis flowmeters) may have a zero offset, which prior art methods initially correct. While this initially determined zero offset can adequately correct measurements under limited circumstances, the zero offset can change over time due to changes in various operating conditions (primarily temperature), resulting in only partial correction. However, other operating conditions may also affect the zero offset, including pressure, fluid density, sensor installation conditions, and so on. Furthermore, the zero offset may change at different rates from one meter to another. This can be of particular concern in situations where more than one meter is connected in series, such that each meter should display the same reading if measuring the same fluid flow rate.

In marine industry applications, seagoing vessels often employ fuel switching schemes, whereby the marine engine operates on different fuel types (or blends thereof). Typically, heavy fuel oil (HFO) and either marine diesel oil (MDO) or marine fuel oil (MFO) are the fuels used. When switching fuel sources, the HFO operating temperature, which is approximately 120-150°C, is changed to the MDO/MFO operating temperature, which is approximately 30-50°C. Due to the approximately 50°C temperature difference between these two operating temperatures, temperature-driven zero-point drift can be a problem.

Therefore, there is a need in the art for a method to determine and compensate for changes in zero offset of a vibration sensor that experiences changes in operating temperature.The present invention overcomes this and other problems and achieves an advance in the art.

Summary of the Invention

According to an embodiment, a method for operating a system configured to consume a fluid and having at least two flow meters is provided. The embodiment includes the following steps:

recirculating the fluid in a closed loop having a supply-side flow meter and a return-side flow meter such that substantially no fluid is consumed;

Measuring fluid flow in a supply-side flow meter and a return-side flow meter;

comparing fluid flow measurement results between a supply-side flow meter and a return-side flow meter;

determining a first differential zero value based on a difference in fluid flow measurements between the supply-side flow meter and the return-side flow meter;

receiving a first temperature sensor signal value;

associating a first differential zero value with the first temperature sensor signal value; and

A first differential zero value associated with the first temperature sensor signal value is stored in the meter electronics.

According to an embodiment, a method for operating a multi-fuel system is provided, the multi-fuel system having an engine, at least two fuel tanks configured to each contain a different fuel, and at least a supply-side flow meter and a return-side flow meter. The embodiment includes the following steps:

recirculating the first fuel type in a closed loop when the engine is not operating such that substantially no fuel is consumed;

measuring a first fuel flow rate in a supply-side flow meter and a return-side flow meter;

comparing first fuel flow measurement results between the supply-side flow meter and the return-side flow meter, and determining a first differential zero value based on a difference in the fuel flow measurement results between the supply-side flow meter and the return-side flow meter;

receiving a first temperature sensor signal value;

associating a first differential zero value with the first temperature sensor signal value and the first fuel type;

storing a first differential zero value associated with the first temperature sensor signal value and the first fuel type in the meter electronics;

recirculating the second fuel type in a closed loop when the engine is not operating such that substantially no fuel is consumed;

measuring a second fuel flow rate in a supply-side flow meter and a return-side flow meter;

comparing second fuel flow rate measurements between the supply-side flow meter and the return-side flow meter, and determining a second differential zero value based on a difference in the fuel flow rate measurements between the supply-side flow meter and the return-side flow meter;

receiving a second temperature sensor signal value;

correlating a second differential zero value with the second temperature sensor signal value and the second fuel type;

A second differential zero value associated with the second temperature sensor signal value and the second fuel type is stored in the meter electronics.

According to an embodiment, a meter electronics for a flow meter is provided, which includes a processing system connected to a system having an engine. According to the embodiment, the meter electronics is configured to:

receiving sensor signals from both the supply-side flow meter and the return-side flow meter when the engine is not operating;

determining a differential zero offset between a supply-side flow meter and a return-side flow meter based on the received sensor signal;

determining a temperature of at least one of a supply side flow meter or a return side flow meter;

Correlating the differential zero offset to temperature; and

The temperature-dependent differential zero offset is stored in the meter electronics.

aspect

According to one aspect, a method for operating a system configured to consume fluid and having at least two flow meters is provided. The method includes the steps of recirculating fluid in a closed loop having a supply-side flow meter and a return-side flow meter such that substantially no fluid is consumed; measuring fluid flow in the supply-side flow meter and the return-side flow meter; comparing the fluid flow measurements between the supply-side flow meter and the return-side flow meter; determining a first differential zero value based on a difference in the fluid flow measurements between the supply-side flow meter and the return-side flow meter; receiving a first temperature sensor signal value; associating the first differential zero value with the first temperature sensor signal value; and storing the first differential zero value associated with the first temperature sensor signal value in meter electronics.

Preferably, a plurality of differential zero point values are determined for the first temperature sensor signal value, each at a different point in time, and the plurality of differential zero point values are stored and associated with the first temperature sensor signal value.

Preferably, this aspect includes the steps of averaging the plurality of differential zero values to calculate an averaged plurality of differential zero values; associating the averaged plurality of differential zero values with a first temperature sensor signal value; and storing the averaged plurality of differential zero values associated with the first temperature sensor signal value in the meter electronics.

Preferably, this aspect comprises the steps of applying a statistical analysis to the plurality of differential zero values, and discarding outlier differential zero values.

Preferably, this aspect includes the steps of operating an engine disposed between a supply side flow meter and a return side flow meter so that fluid is consumed; receiving a temperature sensor signal value from at least one of the supply side flow meter and the return side flow meter while the engine is operating; measuring fluid flow in the supply side flow meter and the return side flow meter while the engine is operating; calculating engine fluid consumption by comparing the fluid flow measurement results between the supply side flow meter and the return side flow meter using an engine fluid consumption equation; applying a differential zero value associated with the temperature sensor signal value in the meter electronics to the engine fluid consumption equation; and outputting an adjusted fluid consumption measurement result corrected for the operating temperature.

Preferably, this aspect includes the following steps: measuring a second fluid flow rate in the supply side flow meter and the return side flow meter; comparing the second fluid flow rate measurement results between the supply side flow meter and the return side flow meter, and determining a second differential zero point value based on the difference in the fluid flow rate measurement results between the supply side flow meter and the return side flow meter; receiving a second temperature sensor signal value from at least one of the supply side flow meter and the return side flow meter; associating the second differential zero point value with the second temperature sensor signal; and storing the second differential zero point value associated with the second temperature sensor signal value in the meter electronics.

Preferably, this aspect includes the steps of: operating an engine disposed between a supply-side flow meter and a return-side flow meter so that fluid is consumed; receiving a temperature sensor signal value from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating; measuring fluid flow in the supply-side flow meter and the return-side flow meter while the engine is operating; calculating engine fluid consumption by comparing the fluid flow measurement results between the supply-side flow meter and the return-side flow meter using an engine fluid consumption equation; applying a differential zero point value associated with the first temperature sensor signal value in the meter electronics to the engine fluid consumption equation if the temperature sensor signal value received from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating is within a threshold value associated with a first temperature sensor signal value in the meter electronics; applying a differential zero point value associated with the second temperature sensor signal value in the meter electronics to the engine fluid consumption equation if the temperature sensor signal value received from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating is within a threshold value associated with a second temperature sensor signal value in the meter electronics; and outputting an adjusted fluid consumption measurement result corrected for the operating temperature.

Preferably, this aspect includes the step of applying an interpolated differential zero value derived from the first temperature sensor signal value and the second temperature sensor signal value in the meter electronics to the engine fluid consumption equation if a temperature sensor signal value received from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating is between a first temperature sensor signal value in the meter electronics and a second temperature sensor signal value in the meter electronics.

Preferably, this aspect includes the step of applying an extrapolated differential zero value derived from the first temperature sensor signal value and the second temperature sensor signal value in the meter electronics to the engine fluid consumption equation if a temperature sensor signal value received from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating is outside a range of a first temperature sensor signal value in the meter electronics and a second temperature sensor signal value in the meter electronics.

According to one aspect, a method for operating a multi-fuel system is provided, the multi-fuel system having an engine, at least two fuel tanks configured to each contain a different fuel, and at least a supply-side flow meter and a return-side flow meter. The method includes the steps of: recirculating a first fuel type in a closed loop when the engine is not operating so that substantially no fuel is consumed; measuring a first fuel flow rate in the supply-side flow meter and the return-side flow meter; comparing the first fuel flow rate measurements between the supply-side flow meter and the return-side flow meter, and determining a first differential zero value based on a difference in the fuel flow rate measurements between the supply-side flow meter and the return-side flow meter; receiving a first temperature sensor signal value; associating the first differential zero value with the first temperature sensor signal value and the first fuel type; storing the first differential zero value associated with the first temperature sensor signal value and the first fuel type in the meter electronics; a second fuel type in a closed loop when the engine is not operating so that substantially no fuel is consumed; measuring the second fuel flow rate in a supply-side flow meter and a return-side flow meter; comparing the second fuel flow rate measurements between the supply-side flow meter and the return-side flow meter and determining a second differential zero value based on a difference in the fuel flow rate measurements between the supply-side flow meter and the return-side flow meter; receiving a second temperature sensor signal value; associating the second differential zero value with the second temperature sensor signal value and the second fuel type; and storing the second differential zero value associated with the second temperature sensor signal value and the second fuel type in the meter electronics.

Preferably, this aspect includes the steps of operating the engine using a first fuel type; measuring a first operating temperature of at least one of the supply side flow meter and the return side flow meter; retrieving a first differential zero point value corresponding to the first operating temperature and the first fuel type; applying the first differential zero point value to an engine fluid consumption equation; and outputting an adjusted fluid consumption measurement result calculated using the engine fluid consumption equation, which is corrected for the first operating temperature and the first fuel type.

Preferably, this aspect includes the steps of converting the fuel type used for engine operation; measuring a second operating temperature of at least one of the supply side flow meter and the return side flow meter; retrieving a second differential zero point value corresponding to the second operating temperature and the second fuel type; applying the second differential zero point value to the engine fluid consumption equation; and outputting an adjusted fluid consumption measurement result calculated using the engine fluid consumption equation, which is corrected for the second operating temperature and the second fuel type.

According to one aspect, meter electronics for a flow meter is provided, comprising a processing system connected to a system having an engine. The meter electronics is configured to: receive sensor signals from both a supply-side flow meter and a return-side flow meter when the engine is not operating; determine a differential zero offset between the supply-side flow meter and the return-side flow meter based on the received sensor signals; determine a temperature of at least one of the supply-side flow meter or the return-side flow meter; associate the differential zero offset with the temperature; and store the differential zero offset associated with the temperature in the meter electronics.

Preferably, the processing system is configured to: determine a first operating temperature of at least one of the supply-side flow meter or the return-side flow meter; compare the first operating temperature to one or more previous temperatures stored in the meter electronics; and if a previously determined zero offset is associated with the first operating temperature, apply the zero offset associated with the first operating temperature to calculations used to determine engine fuel consumption.

Preferably, the processing system is configured to: determine a second operating temperature of at least one of the supply-side flow meter or the return-side flow meter; compare the second operating temperature to one or more previous temperatures stored in the meter electronics; and if a previously determined zero offset is associated with the second operating temperature, apply the zero offset associated with the second operating temperature to calculations used to determine engine fuel consumption.

Preferably, the processing system is configured to: store a plurality of differential zero offsets associated with a plurality of corresponding temperatures of at least one of the supply side flow meter or the return side flow meter; calculate an interpolated zero offset if the measured operating temperature is between at least two of the plurality of corresponding temperatures; and apply the interpolated zero offset associated with the measured operating temperature to calculations for determining engine fuel consumption.

Preferably, the processing system is configured to: store a plurality of differential zero offsets associated with a plurality of corresponding temperatures of at least one of the supply side flow meter or the return side flow meter; calculate an extrapolated zero offset if the measured operating temperature is outside the range of the plurality of corresponding temperatures; and apply the extrapolated zero offset associated with the measured operating temperature to calculations for determining engine fuel consumption.

Preferably, the processing system is configured to switch between a plurality of stored zero offset values associated with respective stored temperatures to correspond to an operating temperature.

According to one aspect, a method for operating a flow meter is provided. The method includes the steps of associating a first zero offset value with a first temperature sensor signal value; storing the first zero offset value associated with the first temperature sensor signal value in meter electronics; associating a second zero offset value with a second temperature sensor signal value; and storing the second zero offset value associated with the second temperature sensor signal value in meter electronics.

Preferably, a method for operating a flow meter includes the steps of measuring an operating temperature of the flow meter; comparing the operating temperature to at least a first zero offset value and a second zero offset value; retrieving a stored zero offset value that most closely corresponds to the operating temperature; applying the stored zero offset value that most closely corresponds to the operating temperature to an operating routine; and outputting an adjusted flow meter measurement result corrected for the operating temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 shows a vibration sensor assembly according to an embodiment of the present invention;

FIG2 shows a fuel system according to an embodiment of the present invention;

FIG3 shows meter electronics according to an embodiment of the present invention;

4 is a flow chart describing a differential zero routine according to an embodiment of the present invention;

5 is a flow chart describing another differential zero routine according to an embodiment of the present invention;

6 is a flow chart describing yet another differential zero routine according to an embodiment of the present invention;

FIG7 is a flow chart describing an operating routine according to an embodiment of the present invention; and

8 is a flow chart describing the operation of a flow meter according to an embodiment of the present invention.

DETAILED DESCRIPTION

Figures 1-8 and the following description depict specific examples for teaching those skilled in the art how to make and use the best mode of the present invention. For the purpose of teaching the principles of the invention, certain conventional aspects have been simplified or omitted. Those skilled in the art will appreciate that variations based on these examples fall within the scope of the present 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 present invention. As a result, the present invention is not limited to the specific examples described below, but is only limited by the claims and their equivalents.

1 illustrates an example of a flow meter 5 in the form of a Coriolis flow meter, which includes a sensor assembly 10 and one or more meter electronics 20. The one or more meter electronics 20 are connected to the sensor assembly 10 to measure properties of the flowing material, such as, for example, density, mass flow rate, volume flow rate, totalized mass flow, temperature, and other information.

Sensor assembly 10 includes a pair of flanges 101 and 101', manifolds 102 and 102', and pipes 103A and 103B. Manifolds 102 and 102' are secured to opposing ends of pipes 103A and 103B. Flanges 101 and 101' of this example are secured to manifolds 102 and 102'. Manifolds 102 and 102' of this example are secured to opposing ends of gasket 106. Gasket 106 maintains a gap between manifolds 102 and 102' in this example to prevent unwanted vibrations in pipes 103A and 103B. Pipes 103A and 103B extend outward from the manifold in a substantially parallel manner. When sensor assembly 10 is inserted into a piping system (not shown) carrying flowing material, the material enters sensor assembly 10 through flange 101, passes through inlet manifold 102 which directs the total amount of material into pipes 103A and 103B, flows through pipes 103A and 103B and back into outlet manifold 102' where it exits sensor assembly 10 through flange 101'.

Sensor assembly 10 includes a driver 104. Driver 104 is secured to pipes 103A and 103B in a position where it can cause pipes 103A, 103B to vibrate in a driven mode. More specifically, driver 104 includes a first driver component (not shown) secured to pipe 103A and a second driver component (not shown) secured to pipe 103B. Driver 104 can include one of many well-known arrangements, such as a magnet mounted to pipe 103A and an opposing coil mounted to pipe 103B.

In this example, the drive mode is the first out-of-phase bending mode, and conduits 103A and 103B are preferably selected and appropriately mounted to inlet manifold 102 and outlet manifold 102' to provide a balanced system having substantially the same mass distribution, moment of inertia, and elastic modulus about bending axes W-W and W'-W', respectively. In this example, where the drive mode is the first out-of-phase bending mode, conduits 103A and 103B are driven by driver 104 in opposite directions about their respective bending axes W-W and W'-W'. A drive signal in the form of an alternating current can be provided by one or more meter electronics 20, such as, for example, via path 110, and passed through the coil to cause both conduits 103A and 103B to oscillate. One of ordinary skill in the art will appreciate that other drive modes can be used within the scope of the present invention.

The illustrated sensor assembly 10 includes a pair of sensors 105, 105' secured to pipes 103A, 103B. More specifically, a first sensor component (not shown) is located on pipe 103A, and a second sensor component (not shown) is located on pipe 103B. In the depicted embodiment, sensors 105, 105' may be electromagnetic detectors, such as sensor magnets and sensor coils, that generate sensor signals representative of the velocity and position of pipes 103A, 103B. For example, sensors 105, 105' may supply the sensor signals to one or more meter electronics via passages 111, 111'. Those skilled in the art will appreciate that the motion of pipes 103A, 103B is proportional to certain properties of the flowing material, such as the mass flow rate and density of the material flowing through pipes 103A, 103B.

It should be appreciated that while the sensor assembly 10 described above includes a dual-flow conduit flowmeter, implementing a single-flow conduit flowmeter is well within the scope of the present invention. Furthermore, while the flow conduits 103A, 103B are shown as including curved flow conduit structures, the present invention can be implemented using a flowmeter including a straight flow conduit structure. Therefore, the specific embodiment of the sensor assembly 10 described above is merely an example and should in no way limit the scope of the present invention.

In the example shown in FIG1 , the one or more meter electronics 20 receive sensor signals from the sensors 105 , 105 ′. Path 26 provides input and output means that allow the one or more meter electronics 20 to interface with an operator. The one or more meter electronics 20 measure characteristics of the flowing material, such as, for example, phase difference, frequency, time delay, density, mass flow rate, volume flow rate, total mass flow rate, temperature, meter verification, and other information. More specifically, the one or more meter electronics 20 receive one or more signals, for example, from the sensors 105 , 105 ′ and one or more temperature sensors 107 , such as resistance temperature devices (RTDs), and use this information to measure characteristics of the flowing material.

The technology used by vibrating sensor assemblies (such as, for example, Coriolis flow meters or densitometers) to measure properties of flowing materials is well understood; therefore, a detailed discussion is omitted for brevity of description.

As briefly discussed above, one problem associated with sensor assemblies, such as Coriolis flowmeters, is the presence of a zero offset, which is the measured time delay of the sensitive element 105, 105' at zero fluid flow. If the zero offset is not taken into account when calculating flow rate and various other flow measurements, the flow measurements will generally include errors. A typical prior art method for compensating for zero offset is to measure an initial zero offset (Δt ₀ ) during an initial calibration process, which typically involves closing a valve and providing a zero flow reference condition. Such calibration processes are generally known in the art and a detailed discussion is omitted for brevity of description. Once the initial zero offset is determined, the flow measurements are corrected during operation by subtracting the initial zero offset from the measured time difference according to equation (1).

in:

= Mass flow rate

FCF = Flow Calibration Factor

Δt _measured = measured time delay

Δt ₀ = initial zero point offset.

It should be appreciated that equation (1) is provided merely as an example and in no way should limit the scope of the present invention.While equation (1) is provided to calculate mass flow rate, it should also be appreciated that various other flow measurements may be affected by zero offset and therefore may also be corrected.

While this method can provide satisfactory results when operating conditions are substantially the same as those present during initial calibration and determination of the zero offset Δt ₀ , in many environments, operating conditions during use differ substantially from those present during calibration. As a result of these changes in conditions, the vibrating flowmeter may experience drift in its zero offset. These issues are particularly pronounced in marine applications utilizing fuels that require substantially different operating temperatures, such as MDO and HFO. In other words, the zero offset can vary from the initially calculated zero offset Δt _0. This drift in the zero offset can severely impact sensor performance, leading to inaccurate measurement results. This is because, in prior art methods, the zero offset used to compensate for time differences measured during operation only includes the initially calculated zero offset and does not account for changes in the zero offset. Other prior art methods require manual recalibration of the sensor. Typically, recalibration requires stopping flow through the sensor to zero the sensor, which is generally impractical for marine fuel system applications. Furthermore, when flow is stopped to perform prior art zero calibration, the temperature of the meter can change rapidly if the ambient temperature differs from the fluid temperature. This may cause unreliable zero point calibration.

FIG2 illustrates a fuel system 200 according to an embodiment. While system 200 is shown as a typical marine fuel system, it should be understood that fuel is merely an example and system 200 is equally applicable to other fluids. Therefore, the use of fuel should not limit the scope of the present invention. Fuel is stored in main tanks 202 and 204. In one embodiment, HFO is stored in the first main tank 202, and MDO is stored in the second main tank 204. Main tanks 202 and 204 are fed into a day tank 206 via fuel lines 203 and 205, respectively. For safety and pollution prevention purposes, day tank 206 is typically sized to store a limited amount of fuel. Day tank 206 prevents excessive fuel from being stored in areas such as a ship's engine room, minimizing the risk of fire or explosion. In the event of a fire, limited fuel availability contributes to reducing the severity of fire-related incidents. Additionally, the day tank 206 receives fuel that has been provided to the engine 208 but not utilized thereby, whereby the return fuel is routed back to the day tank via another fuel line 207. It should be appreciated that while the system 200 shows only one fuel outlet 222 and two flow meters 214, 216, in certain embodiments, there will be multiple fuel outlets and more than two flow meters.

During operation, fuel is typically recirculated from the day tank 206 to the engine 208 or other fuel-consuming equipment, and any unconsumed fuel flows back to the day tank 206 in a closed loop. If the day tank 206 becomes low on fuel, fuel from the main tanks 202, 204 is refilled. A pump 210 provides the necessary movement to pump fuel from the day tank 206 to the engine 208 and back. An inline preheater 212 heats the fuel to a temperature ideal for use by the engine 208. For example, the operating temperature of HFO is generally between approximately 120-150°C, while the operating temperature of MDO/MFO is ideally approximately 30-50°C. The appropriate temperature for a particular fuel allows the viscosity of the fuel to be controlled and maintained within a desired range. The kinematic viscosity of a fuel is a measure of its fluidity at a certain temperature. Because the viscosity of fuel decreases as temperature increases, the viscosity of the fuel at the moment it leaves the engine's fuel injector (not shown) must be within the range specified by the engine manufacturer in order to produce an optimal fuel injection pattern. Viscosity that deviates from the specification results in substandard combustion, energy loss, and potentially deposit formation. Preheater 212 allows for optimal viscosity to be achieved when properly set for the specific fuel being used.

To measure flow parameters such as mass flow rate, inline flow meters are used, for example. Supply-side flow meter 214 is located upstream of engine 208, while return-side flow meter 216 is located downstream of engine 208. Because engine 208 does not consume all the fuel supplied to it via a common fuel rail system (not shown), excess fuel is recirculated through day tank 206 and closed loop 218. Therefore, a single flow meter would not provide accurate flow measurements, particularly those related to engine fuel consumption. Therefore, both supply-side 214 and return-side 216 flow meters (upstream and downstream of engine 208, respectively) are required. According to an embodiment, the difference in flow rates measured by flow meters 214 and 216 is substantially equal to the flow rate of fuel consumed by engine 208. Therefore, the difference in measured flow rates between flow meters 214 and 216 is a value of interest in most applications similar to the configuration shown in FIG. However, it should be noted that the common fuel rail system is used merely as an example and does not limit the scope of the claimed invention. Other fuel systems are contemplated in which fuel is returned and/or recirculated.

Because multiple flow meters 214, 216 are employed, it is critical for accuracy that each meter has an accurately set zero offset, as mentioned in the above description and in equation (1). Even more importantly, the two meters 214, 216 are adjusted to have zero points set relative to each other, and this is called a differential zero. For example, under non-consumption conditions (i.e., the engine 208 is off and fuel is drawn through both flow meters 214, 216 in a closed loop 218), the flow meters should theoretically indicate a zero consumption condition. The differential zero offset includes the initial zero offset of the flow meter combined with the differential error between the two or more flow meters. The differential zero offset can be required in order to generate substantially equal flow rates through the flow meter of interest and the reference flow meter. In other words, referring to equation (1) above, if the same fluid flow rate flows through the calibrated flow meter and the reference flow meter, then two mass flow rates can be generated for each flow meter using equation (1). If we assume that the mass flow rate of the reference flow meter is equal to the mass flow rate of the meter being calibrated, the differential zero offset of the flow meter being calibrated can be calculated. This method finds a new zero offset for the flow meter calibrated to reflect the reference flow rate. This new zero offset is essentially a differential offset. This is shown in equations (2)-(4).

in:

= Reference mass flow rate

= Mass flow rate of the flow meter being calibrated

Δt _0C = Initial zero offset of the flow meter being calibrated

Δt _E = differential error

Δt _c = measured time delay of the flow meter being calibrated

FCF _C = Flow calibration factor of the flow meter being calibrated.

Equation (3) can be further simplified by combining the zero offset of the flow meter being calibrated with the differential error. The result is an equation that defines the differential zero offset, which is shown in equation (4).

in:

Δt _D = Differential zero offset.

Thus, the particular flow meter offset of interest is not an absolute zero offset in the sense of referencing it to zero flow rate, but rather, the zero offset comprises a differential zero offset because it accounts for the difference between the two flow meters 214, 216. When this differential offset is characterized and eliminated, the performance of the differential measurement results for the flow meter pair is greatly improved. It should be appreciated that equation (4) can be further simplified in any number of ways by assuming that certain values (such as the flow calibration factor or the initial zero offset value) remain constant. Therefore, the specific form of equation (4) should not limit the scope of the present invention.

In the system 200 configuration, it is desirable to size the flow meter so that there is very little pressure drop, which translates to relatively low flow rates for the size of the flow meter. At such low flow rates, the time delay between the sensing elements will also be relatively small. With the measured time delay so close to the zero offset, the zero offset of the flow meter can severely impact the accuracy of the meter. It can be readily appreciated that, due to the increased sensitivity to zero offset in the system 200, even small drifts in the zero offset can adversely affect the entire system.

Because the difference in the measurement results is the value of interest, the absolute zero offset of the individual flow meters 214, 216 is not required to correct the measurement results. For example, the return-side flow meter 216 can be referenced relative to the supply-side flow meter 214. Therefore, in embodiments where the zero offset includes a differential zero offset, one of the flow meters can be considered a reference flow meter, with the zero offset of the other flow meter calibrated to match the reference meter. Therefore, the differential zero offset can be calculated using at least equation (3).

Given the wide operating temperature range in dual fuel systems, to achieve a greater level of accuracy, it is necessary in embodiments of system 200 to characterize the differential offset over the range in operating temperature.

FIG3 illustrates meter electronics 20 according to an embodiment of the present invention. Meter electronics 20 may include an interface 301 and a processing system 303. Processing system 303 may include a storage system 304. Storage system 304 may include internal memory, or alternatively, external memory. Meter electronics 20 may generate a drive signal 311 and supply drive signal 311 to driver 104. Additionally, meter electronics 20 may receive sensor signals 310 from flow meters 214, 216, such as pick-off/velocity sensor signals, strain gauge signals, optical signals, or any other signals known in the art. In certain embodiments, sensor signals 310 may be received from driver 104. Meter electronics 20 may operate as a density meter or as a mass flow meter, including as a Coriolis flow meter. It should be appreciated that meter electronics 20 may also operate as some other type of vibration sensor assembly, and the specific examples provided should not limit the scope of the present invention. Meter electronics 20 may process sensor signals 310 to obtain flow characteristics of the material flowing through flow conduits 103A, 103B. In certain embodiments, meter electronics 20 may receive temperature signal 312 , for example, from one or more RTD sensors or other temperature sensors 107 .

Interface 301 can receive sensor signals 310 from driver 104 or sensing elements 105, 105' via leads 110, 111, 111'. Interface 301 can perform any necessary or desired signal conditioning, such as any form of formatting, amplification, buffering, etc. Alternatively, some or all of the signal conditioning can be performed in processing system 303. Additionally, interface 301 can enable communication between meter electronics 20 and external devices. Interface 301 can be capable of any form of electronic, optical, or wireless communication.

In one embodiment, the interface 301 may include a digitizer 302, wherein the sensor signal includes an analog sensor signal. The digitizer 302 may sample and digitize the analog sensor signal and generate a digital sensor signal. The digitizer 302 may also perform any required decimation, wherein the digital sensor signal may be decimated to reduce the amount of signal processing required and to reduce processing time.

The processing system 303 can direct the operation of the meter electronics 20 and process flow measurements from the sensor assembly 10. The processing system 303 can execute one or more processing routines, such as a zero consumption capture routine 313, a differential zero routine 314, a general operation routine 315, and a fuel type signal routine 316, and thereby process the flow measurements to produce one or more flow measurements that are compensated for drift in the zero offset of the flow meter.

According to an embodiment, meter electronics 20 can be configured to measure flow through supply-side flow meter 214 and return-side flow meter 216 as part of a zero consumption capture routine 313. This occurs when engine 208 is not operating but fuel is passing through closed loop 218. According to an embodiment, meter electronics 20 can also measure and store temperature signal 312 and correlate that temperature with the flow rate captured at that temperature.

As an example of a zero consumption capture routine 313, system 200 may include a supply-side flow meter 214 and a return-side flow meter 216, each having (or sharing) meter electronics 20. The meter electronics, if not shared, may communicate with each other via interconnect 220. The return-side flow meter 216 may generate a consumption output, such as a differential mass flow rate or a differential mass flow total, for example, as part of operating routine 315. In one embodiment of operating routine 315, the return flow rate is subtracted from the supply flow rate to provide a consumption measurement. Meter electronics 20 subtracts the two absolute flow signals to produce a differential output, accounting for any signal processing delays between the meters.

The zero consumption capture routine 313 senses when the engine 208 is shut down and fuel is flowing in the closed loop 218. In this case, the temperature signal 312 is saved, and the difference in the zero consumption flow rate is also saved and calculated as part of the differential zero routine 314. Differential zero improves the differential flow calculation performed between the two meters because it mitigates the temperature effects between the meters. This eliminates the need for any zeroing procedures before operation. In the working example, if the engine is shut down, there is still flow through both flow meters 214 and 216—1000 kg/hr (for example purposes). The meters will likely not each accurately display a reading of 1000 kg/hr. Instead, one might display a reading of 999 kg/hr and the other might display a reading of 1001 kg/hr, so the user will see a 2 kg/hr consumption (or production) measurement when the engine is shut down. This 2 kg/hr error will equate to a significant difference over a long period of operation. Thus, at a particular temperature, a 2 kg/hr differential zero point will be saved in the meter electronics and used in the general operating routine 315 as a correction to any flow meter measurement.

Processing system 303 may include a general-purpose computer, a microprocessor system, a logic circuit, or some other general-purpose or custom processing device. Processing system 303 may be distributed among multiple processing devices. Processing system 303 may include any manner of integrated or independent electronic storage media, such as storage system 304.

The processing system 303 processes the sensor signal 310 to, among other things, generate a drive signal 311. The drive signal 311 is supplied to the driver 104 to vibrate the associated flow tube(s), such as the flow tubes 103A, 103B of FIG.

It should be understood that the meter electronics 20 may include various other components and functions generally known in the art. For the sake of brevity, these additional features are omitted from the description and drawings. Therefore, the present invention should not be limited to the specific embodiments shown and discussed.

When processing system 303 generates various flow characteristics (such as, for example, mass flow rate or volume flow rate), errors may be associated with the generated flow rates due to the zero offset of the vibrating flow meter, and more particularly, due to changes or drift in the zero offset of the vibrating flow meter. While the zero offset is typically initially calculated as described above, the zero offset can drift from this initially calculated value due to a number of factors, including changes in one or more operating conditions, particularly the temperature of the vibrating flow meter. Changes in temperature can be due to changes in the fluid temperature, the ambient temperature, or both. In system 200, preheater 212 is primarily responsible for the temperature of the fluid experienced by flow meters 214, 216. Changes in temperature will likely deviate from the reference or calibration temperature T ₀ of the sensor during the initial zero offset determination. According to an embodiment, meter electronics 20 may implement a differential zero routine 314, as described further below.

FIG4 is a flow chart illustrating an embodiment of a routine executed, such as the zero consumption capture routine 313 and/or the differential zero routine 314. At some point, the system 200 is operated in a closed loop zero consumption state 400. In such a state, the supply side flow meter 214 and the return side flow meter 216 each experience fluid flow, but the engine 208 or other fuel consuming device is not operating. Therefore, no fuel is being consumed, and the measured flow rates between the flow meters 214, 216 should be the same. The flow through the flow meters 214, 216 is then measured in step 402, and the temperature of at least one of the flow meters 214, 216 is also measured in step 404. In step 402, the received sensor signals can be processed to determine a first flow rate as determined by the supply side flow meter 214 and a second flow rate as determined by the return side flow meter 216. For example, the first and second flow rates can be determined using equation (1). The received sensor signals may be received during normal operation (e.g., while fluid is flowing through the flow meters 214, 216). The sensor signals may include time delay, phase difference, frequency, temperature, etc. The sensor signals may be processed to determine one or more operating conditions. The one or more current operating conditions may include temperature, fluid density, pressure, drive gain, etc.

The temperature can be determined by processing the sensor signal received in step 404. Alternatively, the one or more operating conditions can be determined based on an external input (not shown), such as an external temperature sensor. For example, an RTD can be used to determine the temperature. For example, the temperature can correspond to the flow meter temperature or the meter electronics temperature. According to one embodiment of the present invention, the temperature is assumed to be substantially the same between flow meters 214, 216. According to another embodiment of the present invention, the difference in temperature between flow meters 214, 216 is assumed to remain substantially constant. In one embodiment, each flow meter 214, 216 includes a separate temperature sensor. In one embodiment, a separate temperature is determined for each flow meter 214, 216, and the temperatures are averaged for calculation purposes. In one embodiment, a separate temperature is determined for each flow meter 214, 216, and each measured temperature is input into the meter electronics 20. In one embodiment, a separate temperature is determined for each flow meter 214, 216, and a single temperature is used for calculation purposes.

One or more sensor signals may be received from the flow meters 214, 216. For example, the sensor signal may be received by the sensor 105, 105' of the supply-side flow meter 214. Because there are multiple flow meters, such as in FIG. 2, sensor signals may be received from both flow meters 214, 216 when fluid is flowing through both flow meters 214, 216. A differential zero value is calculated in step 406 using an equation that is the same or similar to that described above and stored in the meter electronics 20 in step 408. The differential zero value and the corresponding temperature may be stored in a variety of formats, including, for example, a lookup table, a map, an equation, etc., and may be stored in the meter electronics 20, local hardware, software, or a remote hardware/computing device (not shown).

According to an embodiment of the present invention, for example, equations (2)-(4) may be used to determine a differential zero offset. According to an embodiment of the present invention, the determined zero offset may include an initially determined zero offset. This may be the case if the routine of Figures 4-6 is, for example, implemented as part of an initial calibration of a vibrating flow meter. According to another embodiment of the present invention, the determined zero offset may include a subsequently determined zero offset. The subsequently determined differential zero offset may be different from the initially determined zero offset. This may be the case, for example, in particular if the operating conditions differ from the operating conditions when the initial zero offset was determined.

FIG5 is also a flow chart illustrating an embodiment of the executed routines (such as the zero consumption capture routine 313 and/or the differential zero routine 314). As in the other described embodiments, at some point, in step 400, the system 200 is operated in a closed-loop zero consumption state. In this state, the supply-side flow meter 214 and the return-side flow meter 216 are each experiencing fluid flow, but the engine 208 or other fuel-consuming device is not operating. Therefore, no fuel is being consumed, and the measured flow rates between the flow meters 214 and 216 should be the same. The flow rates through the flow meters 214 and 216 are then measured in step 402, and the temperature of at least one of the flow meters 214 and 216 is also measured in step 404. Using an equation similar to or identical to that described above, a differential zero value is calculated based on the measured temperatures in step 500. The differential zero value is stored in the meter electronics 20 in step 504 and associated with the measured temperature in step 508. If multiple differential zero points are measured for a given temperature, the multiple values are averaged to generate an average differential zero point in step 506. The averaged differential zero point is then stored in the meter electronics 20, associated with the given temperature in step 508.

FIG6 is a flow chart illustrating a related embodiment of a routine. As in the other embodiments described, at some point, the system 200 is operated in a closed loop zero consumption state in step 400. In such a state, the supply side flow meter 214 and the return side flow meter 216 each experience fluid flow, but the engine 208 or other fuel consuming equipment is not in operation. Therefore, no fuel is being consumed, and the measured flow rates between the flow meters 214 and 216 should be the same. The flow rates through the flow meters 214 and 216 are then measured in step 402, and the temperature of at least one of the flow meters 214 and 216 is also measured in step 404. Using an equation identical or similar to the equation described above, a differential zero value is calculated based on the measured temperature in step 500. The differential zero value is stored in the meter electronics 20, and in step 502, the differential zero value is associated with the measured temperature. If multiple differential zero points are stored for a given measured temperature, statistical analysis known in the art is applied to the multiple differential zero points in step 600 to determine the presence of any outliers and discard them. An outlier is a differential zero point that is significantly different from the majority of the other differential zero points measured for a given temperature. These values fall outside the overall data trend presented and are a source of inaccuracy. Such statistical analysis includes, but is not limited to, mean, median, standard deviation, correlation coefficient, Chauvel's criterion, Dixon's Q test, Grubbs' test for outliers, quartile analysis, Mahalanobis distance calculation, modified Thompson's τ test, Pierce's criterion, and any other statistical test known in the art. For the multiple differential zero point values that are not discarded, an average is calculated in step 602. This average is then stored in the meter electronics in step 604. Such statistical analysis can also be part of the zero consumption capture routine 313 and/or the differential zero point routine 314.

Advantageously, for example, compensating for the differential zero offset between two or more meters not only compensates for zero differences based on operating conditions but also removes any absolute zero offset differences between the meters that are attributable to installation effects. Furthermore, the differential zero offset need not necessarily be determined when the flow rate through the flow meter is zero, as long as the fluid flowing through the flow meter of interest and the reference flow meter have substantially the same fluid flow rate. Thus, for example, the differential zero offset can be determined whenever the engine is shut down. However, this assumes that any differences between the measured flow rates are due to changes in zero offset and not due to other factors, such as changes in flow calibration factors. The routine of Figures 4-6 can be performed by the manufacturer or by the user after the sensors have been installed. Furthermore, the routine of Figures 4-6 can be implemented when the flow rates through the two or more flow meters 214, 216 are substantially the same (including zero fluid flow rate).

The routine illustrated by Figures 4-6 can be performed when a fluid-consuming device, such as an engine, is off. In other embodiments, the routine can be performed when it is desired that the flow rates measured by flow meters 214, 216 include the same measurement results, such as during closed loop operation. Therefore, it should be appreciated that the flow through flow meters 214, 216 does not necessarily include zero flow, and in many embodiments will not include zero flow during the routine illustrated by Figures 4-6.

According to an embodiment of the present invention, the differential zero consumption capture routine 313 can be performed after an initial calibration of the vibrating flow meter, or can include part of the initial calibration of the vibrating flow meter. The zero consumption capture routine 313 can be used to generate a correlation between the zero offset of the vibrating flow meter and one or more operating conditions of the vibrating flow meter. The zero offset can include an absolute zero offset or a differential zero offset, as described above.

Once the differential zero offset is associated with a specific temperature, the measured operating temperature can be compared to the temperature associated with the zero offset stored in the meter electronics 20 to determine the appropriate zero offset and apply it to the flow determination equation. According to embodiments of the present invention, the corrected differential zero offset can provide a more accurate determination of various flow characteristics, allowing the meter electronics 20 to output corrected flow measurements/characteristics. In one embodiment, the corrected differential zero offset can provide a more accurate determination of engine fuel consumption.

According to an embodiment of the present invention, the zero offset determined by the routines illustrated by Figures 4-6 can be used during normal operation to determine a differential zero, as indicated by the routine illustrated in Figure 7. More specifically, the zero offset can be used to determine a differential zero offset between the supply-side flow meter 214 and at least a second flow meter (such as the return-side flow meter 216) based on the measured operating temperature.

In yet another embodiment, as illustrated by FIG. 7 , system 200 is operated in step 700 such that fluid is consumed, and system 200 may include an embodiment of general operating routine 315 . In one embodiment, engine 208 is positioned between at least two flow meters 214 , 216 , and the fluid being consumed is fuel for engine 208 . The flow rate of the fluid through the two flow meters 214 , 216 is measured in step 702 , as is the temperature of at least one of the flow meters measured in step 704 . Meter electronics 20 determines in step 706 whether there is any stored differential zero value corresponding to the measured temperature (as measured by at least one of flow meters 214 , 216 ). If a stored differential zero value is associated with the temperature of at least one of flow meters 214 , 216 , the differential zero value is applied to the flow meter calculations in step 708 . The rate of engine fuel consumption is then calculated in step 710 by comparing the fluid flow measurements between supply-side flow meter 214 and return-side flow meter 216 using any known fluid consumption equation. The adjusted engine fluid consumption, corrected by applying the appropriate stored differential zero value, is then output in step 712. However, if there is no stored differential zero value 706 corresponding to the temperature as measured by at least one of flow meters 214, 216, at least two closest stored differential values are identified in step 714. A theoretical differential zero value is then calculated in step 716 by interpolating or extrapolating at least two of the closest stored differential values corresponding to the measured temperature. This theoretical differential zero is then applied to the flow meter calculations in step 718. As above, the rate of engine fuel consumption is then calculated by comparing the fluid flow measurements between the supply-side flow meter 214 and the return-side flow meter 216 using any known fluid consumption equation 710. The adjusted engine fluid consumption, corrected by applying the appropriate stored differential zero value, is then output 712. It should be appreciated that in many cases, the exact measured operating conditions may not be stored as relevant values. For example, if the measured operating conditions include a temperature of 20 ^° C and the stored zero offset has corresponding zero offset values for temperatures of 10 ^° C and 30 ^° C, then an appropriate differential zero offset value may be interpolated from the two available temperatures.

A differential zero routine 314 can be performed to calibrate the differential zero offset between two or more flow meters. Thus, the differential zero routine 314 may not necessarily calibrate the flow meters to display an accurate absolute mass flow rate; rather, the flow meters can be calibrated so that the differential reading between the two is accurate. For example, if the true flow rate through the supply-side flow meter 214, as determined by a calibrator or similar device, is 2000 kg/hour and the flow rate of the fluid passing through the return-side flow meter 216 is 1000 kg/hour, it would be desirable to have the difference between the return-side flow meter 216 and the supply-side flow meter 214 equal to 1000 kg/hour. However, in many embodiments, it may be acceptable to calibrate the return-side flow meter 216 to display a reading of 1020 kg/hour if the supply-side flow meter 214 measures a flow rate of 2020 kg/hour. Thus, while the absolute flow rate through each meter may not be accurate, the differential reading is accurate or at least within an acceptable error range. It should be appreciated that the above-mentioned values are merely examples and should in no way limit the scope of the present invention.

Advantageously, a differential zero offset can be generated using the stored offset correlation and the measured operating conditions. The differential zero offset can be determined without having to zero the vibrating flow meter. The differential zero offset can be determined without having to stop fluid flow. Instead, the differential zero offset can be determined simply by comparing the measured operating temperature with the stored differential zero offset correlation.

In certain embodiments, a fuel type signal 316 is provided to meter electronics 20. Each fuel type may have a separate associated differential zero offset and associated temperature stored in the meter electronics.

In some embodiments, the determined operating temperature may be the same as or within a threshold difference of the operating conditions present during calibration. Thus, in some embodiments, the measured operating temperature may be compared to the initial calibration operating conditions and the associated zero offset. If the difference is less than the threshold difference, the differential zero routine may not attempt to retrieve the differential zero offset, and may instead use the zero offset of the initial calibration.

It can be readily appreciated that as more differential zero values are determined at various points in time and at various operating temperatures, the fluid consumption measurement becomes more accurate.

It will also be appreciated that multiple zero offsets can be stored for multiple temperatures for use with a single flow meter. Because flow meters are often required to operate within a certain temperature range, the zero point of the meter may drift as the operating temperature changes. Therefore, different zero offsets can be calculated and saved for different temperatures and stored in the meter electronics 20. For example, if a meter has a zero offset initially captured at 30°C and is then operated at 60°C, the meter may report a flow rate that is less accurate than expected. However, if the meter electronics 20 applies a zero offset that was captured or preset for the 60°C temperature point, the accuracy of the flow meter will increase. In such a case, one or more sensor signals can be received from flow meters 214, 216. Using equations similar to or identical to those described above, a zero offset value for a single meter can be determined and stored in the meter electronics 20. This zero offset value is correlated with the corresponding temperature, which can also be stored in the meter electronics 20.

According to an embodiment of the present invention, the zero offset may include an initially determined zero offset. This may be the case if, for example, the routine is implemented as part of an initial calibration of the flow meter. According to another embodiment of the present invention, the zero offset may include a subsequently determined zero offset. This subsequent zero offset may differ from the initially determined zero offset. This may be the case, for example, particularly if the operating conditions differ from those at the time the initial zero offset was determined. The user may record the subsequently determined zero offset as needed due to changing operating conditions.

FIG8 illustrates an example of a method for operating a flow meter, contemplated as an embodiment. In step 800, a first zero offset value is associated with a first temperature sensor signal value. In step 802, the first zero offset value is associated with the first temperature sensor signal value and stored in the meter electronics 20. Various formats, including lookup tables, maps, equations, and the like, can be stored in the meter electronics 20, local hardware, software, or remote hardware/computing devices (not shown). In step 804, a second zero offset value is associated with the second temperature sensor signal value, and in step 806, the second zero offset value is stored in the meter electronics 20. In step 808, the operating temperature of the flow meter is measured. The temperature can be determined by processing the sensor signal. Alternatively, the temperature can be determined based on an external input (not shown), such as an external temperature sensor. For example, an RTD can be used to determine the temperature. For example, the temperature can correspond to the flow meter temperature or the meter electronics temperature. In step 810, the operating temperature is compared to at least the first zero offset value and the second zero offset value. While only two temperature-dependent zero offsets are mentioned for simplicity, numerous zero offsets at numerous temperatures are contemplated. Additionally, multiple zero offsets can be calculated for a particular temperature, and statistical analysis can be applied to these multiple measurements to reflect a more accurate zero offset for the particular temperature. An example, without limitation, is a simple mean calculation. In step 812, the stored zero offset value that most closely corresponds to the operating temperature is retrieved. The retrieved stored zero offset value that most closely corresponds to the operating temperature is applied to the operating routine in step 814, and the adjusted flow meter measurement corrected for the operating temperature is output in step 816.

The present invention, as described above, provides various methods for determining and compensating for changes that may occur in the differential zero offset of a vibrating flow meter, such as a Coriolis flow meter. While the various embodiments described above are directed to flow meters, and in particular Coriolis flow meters, it should be appreciated that the present invention should not be limited to Coriolis flow meters, but rather the methods described herein can be utilized with other types of flow meters or other vibrating sensors that lack some of the measurement capabilities of a Coriolis flow meter.

The detailed description of the above embodiments is not an exhaustive description of all embodiments contemplated by the inventors within the scope of the present invention. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be combined or eliminated in various ways to create further embodiments, and such further embodiments fall within the scope and teachings of the present invention. It will also be apparent to those skilled 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 present invention.

Therefore, although specific embodiments of the present invention and examples thereof are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present invention, as will be appreciated by those skilled in the relevant art. The teachings provided herein may be applied to other vibration sensors, not just to the embodiments described above and shown in the accompanying drawings. Accordingly, the scope of the present invention should be determined in accordance with the following claims.

Claims (12)

1. A method for operating a system configured to consume fluid, the system having at least two flow meters, the method comprising the steps of: The fluid is recirculated in a closed loop with a supply-side flow meter and a return-side flow meter, so that virtually no fluid is consumed. Measure fluid flow rate in both supply-side and return-side flow meters; Compare the fluid flow measurement results between the supply-side flow meter and the return-side flow meter; The first differential zero point value is determined based on the difference in fluid flow measurement results between the supply-side flow meter and the return-side flow meter; Receive the signal value from the first temperature sensor; Receive the first fuel type signal; The first differential zero-point value is correlated with the first temperature sensor signal value and the first fuel type signal; The first differential zero-point value, associated with the first temperature sensor signal value and the first fuel type signal, is stored in the instrument electronics. An engine (208) is positioned between the supply-side flow meter (214) and the return-side flow meter (216) to consume fluid; The second temperature sensor signal value is received from at least one of the supply-side flow meter and the return-side flow meter while the engine is operating; Receive the second fuel type signal; Fluid flow is measured in both the supply-side and return-side flow meters while the engine is running; The fluid consumption of the engine (208) is calculated using the engine fluid consumption equation by comparing the fluid flow measurement results between the supply-side flow meter (214) and the return-side flow meter (216); Determine whether there are any stored differential zero-point values corresponding to the second temperature sensor signal value and the second fuel type signal; If such a stored differential zero-point value exists, the differential zero-point value associated with the second temperature sensor signal value and the second fuel type signal value in the instrument electronics is applied to the engine fluid consumption equation; If no such stored differential zero-point value exists, a theoretical differential zero-point value is calculated using at least two of the closest stored differential zero-point values corresponding to the second temperature sensor signal value and the second fuel type signal, and this theoretical differential zero-point value is applied to the engine consumption equation; and Outputs adjusted fluid consumption measurements corrected for operating temperature and fuel type. 2. The method of claim 1 for operating a system configured to consume fluid, wherein a plurality of differential zero-point values are determined for a first temperature sensor signal value, each differential zero-point value at a different time point, and the plurality of differential zero-point values are stored and associated with the first temperature sensor signal value. 3. The method of claim 2 for operating a system configured to consume fluid, comprising the following steps: The average of the multiple difference zero-point values is calculated to obtain the average multiple difference zero-point values; The averaged multiple differential zero-point values are correlated with the signal value of the first temperature sensor; The average multiple differential zero-point values associated with the first temperature sensor signal value are stored in the instrumentation electronics. 4. The method of claim 1 for operating a system configured to consume fluid, comprising the following steps: While the engine is running, it receives another temperature sensor signal value from at least one of the supply-side flow meter and the return-side flow meter; Receive signal for another fuel type; Fluid flow is measured in both the supply-side and return-side flow meters while the engine is running; If, while the engine is operating, the value of another temperature sensor signal associated with the other fuel type signal received from at least one of the supply-side flow meter and the return-side flow meter is within a threshold value associated with the first temperature sensor signal value in the instrumentation electronics, then the differential zero-point value associated with the first temperature sensor signal value in the instrumentation electronics is applied to the engine fluid consumption equation. If, while the engine is operating, the value of another temperature sensor signal associated with the other fuel type signal received from at least one of the supply-side flow meter and the return-side flow meter is within a threshold value associated with a second temperature sensor signal value in the instrumentation electronics, then the differential zero-point value associated with the second temperature sensor signal value in the instrumentation electronics is applied to the engine fluid consumption equation. 5. The method of claim 1 for operating a system configured to consume fluid, the system comprising an engine and at least two fuel tanks each configured to contain a different fuel: The step of recirculating fluid in a closed loop includes recirculating a first type of fuel in a closed loop when the engine is not in operation, so that virtually no fuel is consumed. The step of measuring fluid flow includes measuring the first fuel flow in both the supply-side flow meter and the return-side flow meter; The step of comparing fluid flow measurement results includes comparing a first fuel flow measurement result between the supply-side flow meter and the return-side flow meter, and determining a first differential zero-point value based on the difference in the fuel flow measurement results between the supply-side flow meter and the return-side flow meter; The first differential zero-point value is associated with the first fuel type; When the engine is not in operation, the second type of fuel is recirculated in a closed loop, so that virtually no fuel is consumed. The second fuel flow rate is measured in both the supply-side flow meter and the return-side flow meter; The second fuel flow measurement results between the supply-side flow meter and the return-side flow meter are compared, and the second differential zero-point value is determined based on the difference in the fuel flow measurement results between the supply-side flow meter and the return-side flow meter; Receive the signal value from the second temperature sensor; Associate the second differential zero-point value with the second temperature sensor signal value and the second fuel type; and The second differential zero-point value, associated with the second temperature sensor signal value and the second fuel type, is stored in the instrument electronics. 6. The method of claim 5 for operating a system configured to consume fluid, comprising the following steps: Use the first type of fuel to operate the engine; The first operating temperature of at least one of the supply-side flow meter and the return-side flow meter is measured; and Retrieve the first differential zero-point value corresponding to the first operating temperature and the first fuel type; The first difference zero-point value is applied to the engine fluid consumption equation; and The output is an adjusted fluid consumption measurement calculated using the engine fluid consumption equation, corrected for the first operating temperature and the first fuel type. 7. The method of claim 6 for operating a system configured to consume fluid, comprising the steps of: Change the fuel type used for engine operation to a second fuel type; Measuring the second operating temperature of at least one of the supply-side flow meter and the return-side flow meter; and Retrieve the second differential zero-point value corresponding to the second operating temperature and the second fuel type; The second difference zero-point value is applied to the engine fluid consumption equation; and The output is an adjusted fluid consumption measurement calculated using the engine fluid consumption equation, corrected for the second operating temperature and the second fuel type. 8. An instrumentation electronics device (20) for flow meters (214, 216), comprising a processing system (303) connected to a system (200) having an engine (208), the instrumentation electronics device (20) being configured to: Sensor signals (310) are received from both the supply-side flow meter (214) and the return-side flow meter (216) when the engine (208) is not operating. The differential zero offset value between the supply-side flow meter (214) and the return-side flow meter (216) is determined based on the received sensor signal (310); Determine the temperature of at least one of the supply-side flow meter (214) or the return-side flow meter (216); Receive fuel type signal; Correlating the differential zero-point offset value with temperature and fuel type signals; and The differential zero offset values associated with the temperature and fuel type signals are stored in the instrument electronics (20); Determine the first operating temperature of at least one of the supply-side flow meter (214) or the return-side flow meter (216); Receive the first operational fuel type signal; The first operating temperature and first operating fuel type signals are compared with one or more previous temperatures stored in the instrumentation electronics (20); and If the previously determined differential zero-point offset value is associated with the first operating temperature and the first operating fuel type signal, then the differential zero-point offset value associated with the first operating temperature and the first operating fuel type signal is applied to the calculation to determine engine fuel consumption. If there is no previously determined differential zero-point offset value associated with the first operating temperature and the first operating fuel type signal, a theoretical differential zero-point offset value is calculated using at least two of the closest stored differential zero-point offset values corresponding to the first operating temperature and the first operating fuel type signal, and the theoretical differential zero-point offset value is applied to the engine fluid consumption equation to calculate engine fuel consumption. 9. The instrumentation electronics (20) for flow meters (214, 216) according to claim 8, wherein the processing system (303) is configured to: Determine the second operating temperature associated with the first operating fuel type signal for at least one of the supply-side flow meter (214) or the return-side flow meter (216); The second operating temperature is compared with one or more previous temperatures stored in the instrumentation electronics (20) that are associated with the first operating fuel type signal; and If the previously determined differential zero-point offset value is associated with the second operating temperature and the first operating fuel type signal, then the differential zero-point offset value associated with the second operating temperature and the first operating fuel type signal is applied to the calculation to determine engine fuel consumption. 10. The instrumentation electronics (20) for flow meters (214, 216) according to claim 8, wherein the processing system (303) is configured to: Store multiple differential zero offset values associated with multiple corresponding temperatures of at least one of the supply-side flow meter (214) or the return-side flow meter (216), the multiple corresponding temperatures being associated with a first operating fuel type signal; If the measured operating temperature falls between at least two of the plurality of corresponding temperatures associated with the first operating fuel type signal, then the interpolated differential zero-point offset value is calculated; and The interpolated differential zero-point offset value associated with the measured operating temperature, which is associated with the first operating fuel type signal, is used in the calculation to determine engine fuel consumption. 11. The instrumentation electronics (20) for flow meters (214, 216) according to claim 8, wherein the processing system (303) is configured to: Store multiple differential zero offset values associated with a plurality of corresponding temperatures of at least one of the supply-side flow meter (214) or the return-side flow meter (216); If the measured operating temperature is outside the range of the plurality of corresponding temperatures, then the extrapolated differential zero offset value is calculated; and The extrapolated differential zero-point offset value associated with the measured operating temperature is used in the calculation to determine engine fuel consumption. 12. The instrumentation electronics (20) for flow meters (214, 216) according to claim 9, wherein the processing system (303) is configured to: The system converts between multiple stored differential zero offset values associated with the corresponding stored temperature to correspond to the operating temperature.