CN100350223C - Thermal flowmeter - Google Patents
Thermal flowmeter Download PDFInfo
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- CN100350223C CN100350223C CNB038204169A CN03820416A CN100350223C CN 100350223 C CN100350223 C CN 100350223C CN B038204169 A CNB038204169 A CN B038204169A CN 03820416 A CN03820416 A CN 03820416A CN 100350223 C CN100350223 C CN 100350223C
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/6845—Micromachined devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
- G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction
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- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
- Details Of Flowmeters (AREA)
Abstract
A thermal flowmeter comprises a thermal flow sensor having first and second temperature detection elements (Ru, Rd) disposed in the direction of flow of fluid with a heater element (Rh) disposed therebetween, a first temperature sensor (12a) for detecting the temperature of the fluid flowing in a pipe (10), a second temperature sensor (12b, 12c) for detecting the pipe temperature, wherein the flow rate of the fluid is measured from the difference in detection output between the first and second temperature detection elements, while the amount of flow rate correction is found from a temperature difference correction table (24) according to the difference between the pipe temperature and the fluid temperature, the amount of flow rate correction being used to correct the measured fluid flow rate, which correction is capable of eliminating the thermal effect on flow rate measurement from the external environment so as to improve the measurement accuracy.
Description
Technical field
The present invention relates to flowmeter, particularly relate to and to make the fluid flow that flows through in the pipeline not be subjected to the influence of external environment condition, the thermal flowmeter of measuring to high precision.
Background technology
Flow totalizer comprises the flow sensor that the instantaneous delivery that flows through the fluid of fluid passage is measured, and measures integrated flux according to instantaneous delivery, wishes to have high measuring accuracy.Particularly, gas meter, flow meter is owing to be the combustion gas use amount (integrated flux) that becomes the foundation of calculating the combustion gas usage charges with flowing through combustion gas instantaneous delivery in the Gas Pipe through for example accumulating in 1 month, measuring thus, therefore exigent measuring accuracy.
So, in the flow totalizer of nearest gas meter, flow meter etc., use the high thermal flow rate sensor of measuring accuracy usually.Thermal flow rate sensor as shown in Figure 5, flowing through a pair of detector unit Ru, the Rd that setting separated from each other is made of the temperature detecting resistance body on the direction F at fluid on the silicon base B, constitute like this as vane (sensorchip) 1, be arranged between detector unit Ru, the Rd at the heating element Rh that will constitute by heating resistor on the silicon base B, and will be provided with away from heating element Rh by the detector unit Rr that the temperature detecting resistance body constitutes.This vane 1 is installed in the pipeline 10 as shown in Figure 6, and at this moment, detector unit Ru, Rd, Rr and heating element Rh dispose facing to the fluid passage that is formed by pipeline 10.
When flowing through fluid in the pipeline 10, utilize detector unit Ru, Rd, Rr to detect temperature by near the fluid it.And during detected temperatures, Rh switches on heating element.The method of this energising is opened as described in the 2003-121232 communique as the spy, is to use the heat driven circuit with the bridge diagram that comprises heating element Rh and detector unit Rr.The heat driven circuit is according to bridge output voltage, and the impressed voltage of bridge diagram is carried out FEEDBACK CONTROL, by like this heating temp of heating element Rh being remained on uniform temperature, makes it be higher than the fluid temperature (F.T.) that detects by detector unit Rr.
Heat by heating element Rh sends passes to detector unit Ru, Rd through silicon base B or along this fluid that flows through.General longshore current body flows through direction F, pass at the heat transfer capacity of the detector unit Rd of the downstream side of heating element Rh than the heat transfer capacity height that passes to the detector unit Ru of upstream side, and the difference of heat transfer capacity increases along with the increasing of fluid flow.Therefore, the fluid temperature (F.T.) height that the fluid temperature (F.T.) ratio that detects by detector unit Rd detects by detector unit Ru, the difference of two detected temperatures increases along with the increasing of fluid flow.
It is situation about changing according to fluid flow as mentioned above that the thermal flowmeter that comprises thermal flow rate sensor shown in Figure 5 utilizes the difference of the detected temperatures of detector unit Ru, Rd, carries out flow measurement according to the difference of this detected temperatures.
The vane 1 that constitutes thermal flow rate sensor is installed in as mentioned above in the pipeline 10 and uses.And, each in pipeline 10, vane 1 is installed, just vane 1 and pipeline 10 must be carried out heat insulationly, for example, vane 1 is fixed in the pipeline 10 via the base 2 of Kovar alloy composition with by the insulator 3 that glass etc. is formed.In Fig. 6, the sensor line plate (sensor stand sensor blanket) of the above-mentioned heat driven circuit of reference number 4 expression installations etc., 5 expressions are with the O shape circle of sensor line plate 4 with pipeline 10 sealings, and 6 represent the fixed screw of sensor line plates 4.
But, even applied these heat insulation measures, can not deny be subjected to external environment condition for example outside under temperature degree or the influence at sunshine, the temperature of base 2 can change.Therefore, the temperature that is fixed in the vane 1 of base 2 changes along with the variation of external environment condition, and the temperature that detects by the detector unit Rr on the vane 1 is affected.
As mentioned above, because the control of switching on, be used for making the heating temp of heating element Rh than the high uniform temperature of fluid temperature (F.T.), so must represent fluid temperature (F.T.) exactly.However, be subjected to as mentioned above under the situation of external environment influence in the detected temperatures of detector unit Rr, detected temperatures is higher than fluid temperature (F.T.) sometimes, and detected temperatures is lower than fluid temperature (F.T.) sometimes, can not represent fluid temperature (F.T.) exactly.And when switching on control according to inaccurate detected temperatures, the heating temp of heating element Rh just produces deviation for the set point of temperature than the high uniform temperature of fluid temperature (F.T.).
For example, as shown in Figure 7, be controlled in the thermal flowmeter than the structure of the set point of temperature (for example 65 ℃) of the high uniform temperature of fluid temperature (F.T.) (for example 20 ℃) (for example 45 ℃) having heating temp with heating element Rh, because the influence at outer temperature degree or sunshine etc. supposes that the detected temperatures of detector unit Rr is only higher for example 1 ℃ than fluid temperature (F.T.).Even in this case, because the energising of control heating element Rh, make the heating temp of heating element Rh than the high uniform temperature of detected temperatures of detector unit Rr, so the heating temp of heating element Rh is 66 ℃ just than for example 1 ℃ of set point of temperature height.
On the other hand, by the flow measurement that thermal flowmeter carries out, be to be under the febrile state of set point of temperature at heating element Rh to carry out for prerequisite.Therefore, the influence that is subjected to external environment condition in the detected temperatures because of detector unit Rr can not be measured exactly and be made the heating temp of heating element Rh depart under the situation of set point of temperature, and the flow measurement of being undertaken by thermal flowmeter just produces error.
Summary of the invention
The object of the present invention is to provide the influence that can not be subjected to external environment condition to measure fluid flow and thermal flowmeter simple in structure accurately.
In order to achieve the above object, the invention provides a kind of thermal flowmeter, have and be included in fluid and flow through the 1st and the 2nd detector unit and the heating element that between two these detector units, is provided with of setting separated from each other on the direction and be installed in the ducted thermal flow rate sensor that fluid flows through, during driving heating element, measure fluid flow according to the temperature that detects respectively by the 1st and the 2nd detector unit.The characteristics of this thermal flowmeter are, comprise and detect the 1st temperature sensor that flows through the fluid temperature (F.T.) in the pipeline; The 2nd temperature sensor of detector tube channel temp; And according to poor, the temperature difference correcting device of asking for correction of the fluid temperature (F.T.) that detects by the 1st temperature sensor and the pipe temperature that detects by the 2nd temperature sensor.
In thermal flowmeter of the present invention, for example drive heating element, make the high uniform temperature of fluid temperature (F.T.) that its heating temp detects than detector unit Rr or the 1st temperature sensor by Fig. 5 (among the present invention, though can remove detector unit Rr, also can use) with the 1st temperature sensor.At this moment, according to the structure of thermal flowmeter, the detected temperatures of detector unit Rr or the 1st temperature sensor might be subjected to the influence of the external environment condition at outer temperature degree or sunshine etc.In existing thermal flowmeter, influence because of external environment condition, produced the flow measurement error, but in the present invention, be subjected to the influence of external environment condition, make the detected temperatures of detector unit Rr or the 1st temperature sensor produce under the situation of error, ask for modified value, can remove the influence of external environment condition flow measurement according to this modified value of trying to achieve according to its detected temperatures (fluid temperature (F.T.)) and the difference of the pipe temperature that detects by the 2nd temperature sensor.
That is, for example outer temperature degree of external environment condition or sunshine etc. have been to having installed the pipeline generation effect of thermal flow rate sensor, and then by the effect to this pipeline, have influence on flow measurement, and the influence of external environment condition displays with the variation of pipe temperature.This point because the present invention uses the correction of considering pipe temperature, therefore can be removed the influence of external environment condition for flow measurement.Particularly, owing to ask for correction according to the fluid temperature (F.T.) (detected temperatures of the 1st temperature sensor) and the difference of pipe temperature, therefore can remove the influence of external environment condition to the detected temperatures of the 1st temperature sensor, flow measurement is not carried out by the influence of external environment condition can accurately thus.And, for thermal flowmeter of the present invention, for example can be achieved by the 2nd temperature sensor and temperature difference correcting device are added in the existing thermal flowmeter, structure is very simple.
Among the present invention, best, the temperature difference correcting device is asked for the flow correction amount as above-mentioned correction according to the fluid temperature (F.T.) that detects by the 1st temperature sensor and the difference of the pipe temperature that detects by the 2nd temperature sensor.And, use this flow correction amount, revise the measured fluid flow of temperature that detects according to by the 1st and the 2nd detector unit.
According to this optimal morphology, make the heating temp of heating element produce deviation in influence to set point of temperature because of external environment condition, each detected temperatures of the 1st and the 2nd detector unit produces under the situation of error, revise with the flow correction amount according to the inaccurate fluid flow that two detected temperatures (for example two detected temperatures is poor) will be measured, also can ask for fluid flow accurately simply.
Among the present invention, best, the temperature difference correcting device comprises the temperature difference correction chart that the flow correction amount is represented as the function of the difference of fluid temperature (F.T.) and pipe temperature and fluid flow, the pipe temperature that detects according to the fluid temperature (F.T.) that detects by the 1st temperature sensor, by the 2nd temperature sensor and measure fluid flow by the temperature that the 1st and the 2nd detector unit detects is asked for described flow correction amount according to the fluid flow of this measurement from the temperature difference correction chart.
According to this optimal morphology, owing in advance the relation of temperature difference (fluid temperature (F.T.) and pipe temperature poor) and fluid flow and flow correction amount is for example asked for by experiment, generate temperature difference correction chart in advance, therefore can from the temperature difference correction chart, easily ask for the flow correction amount according to fluid temperature (F.T.), pipe temperature and measurement fluid flow with the function representation flow correction amount of temperature difference and fluid flow.And then fluid flow is measured in the correction of use traffic correction, can promptly measure fluid flow accurately.Therefore, can be with short interval measurement instantaneous delivery, and can measure integrated flux more accurately.
Perhaps, the temperature difference correcting device comprises the temperature difference correction chart that the flow correction amount of per unit temperature difference is represented as the function of the difference of fluid temperature (F.T.) and pipe temperature and fluid flow, the pipe temperature that detects according to the fluid temperature (F.T.) that detects by the 1st temperature sensor, by the 2nd temperature sensor and measure fluid flow by the temperature that the 1st and the 2nd detector unit detects is measured to such an extent that fluid flow is asked for the flow correction amount of per unit temperature difference from the temperature difference correction chart according to this.Then, will multiply each other with the difference of the pipe temperature that detects by the 2nd temperature sensor and the flow correction amount of per unit temperature difference, ask for the flow correction amount by the fluid temperature (F.T.) that the 1st temperature sensor detects.
The flow correction principle of this optimal morphology is as follows.Promptly, the output of thermal flow rate sensor when having temperature difference between fluid temperature (F.T.) and the pipe temperature is to change on the basis of the sensor output when not having such temperature difference, but intrinsic understanding according to present inventors, though the output variation of thermal flow rate sensor changes according to temperature difference, but the output variation of per unit temperature difference not too depends on temperature difference, is constant haply.This optimal morphology is used the flow correction amount of such and opposite in sign identical with output variation size, carries out flow correction.
And, according to this optimal morphology,, can ask for the flow correction amount by this easy method that multiplies each other of the flow correction amount with the difference of fluid temperature (F.T.) and pipe temperature and per unit temperature difference based on above-mentioned flow correction principle.
Perhaps, the temperature difference correcting device also can be asked for the temperature correction according to the difference of fluid temperature (F.T.) and pipe temperature.In this case, in the thermal flowmeter, for example drive heating element, make the target heating temp of the heating element asked for according to the detected temperatures of the 1st temperature sensor revise, reach revised target heating temp by the temperature correction.Its result, owing to can prevent the heating temp that the influence because of external environment condition produces and the deviation of set point of temperature, therefore can remove the error of the detected temperatures of the 1st and the 2nd detector unit that the deviation because of heating temp produces, measure fluid flow exactly.
Best, the 1st temperature sensor is arranged to detect the fluid temperature (F.T.) of the central portion in the pipeline.According to this optimal morphology, reduced the possibility that the fluid temperature (F.T.) that detects by the 1st temperature sensor is subjected to the influence of external environment condition widely.Like this, the fluid temperature (F.T.) of the thermal flowmeter of this optimal morphology by central portion in pipeline detects and reduces the influence of external environment condition for flow measurement, particularly, make the 1st temperature sensor have the structure of the environment temperature measuring ability of existing detector unit Rr by formation, add the correction of revising according to the difference of fluid temperature (F.T.) and pipe temperature and remove influence, can improve the flow measurement precision external environment condition.
Best, the 2nd temperature sensor is arranged to detect the wall surface temperature of pipeline.External environment condition is as mentioned above owing to influence flow measurement by the effect for pipeline, so the influence of external environment condition shows the variation of duct wall surface temperature.According to this optimal morphology, be to ask for correction, and, can positively remove the influence of external environment condition flow measurement by using such correction according to the duct wall surface temperature of representing the external environment influence degree well.And the setting of the 2nd temperature sensor that is used to detect the pipeline wall surface temperature is simpler comparatively speaking, helps to simplify the structure of thermal flowmeter.
Best, thermal flowmeter is included in a plurality of the 2nd temperature sensors (for example, 2 the 2nd temperature sensors that are provided with respectively in the both sides of the perpendicular line of the cross-section center by pipeline) of setting separated from each other on the peripheral direction of pipeline.The multiple-way duct temperature that the temperature difference correcting device will detect by a plurality of the 2nd temperature sensors is in addition average, in the hope of being averaged pipe temperature, and poor according to fluid temperature (F.T.) that detects by the 1st temperature sensor and average tube channel temp, ask for correction.
External environment condition is not necessarily to all evenly generation effects of whole periphery of pipeline that thermal flowmeter is installed.For example, when exposed tube is provided with out of doors, pipeline, being subjected to the direct light illuminated portion is different with the pipe temperature that is not subjected to the illumination part.Under the situation that external environment condition acts on unevenly to pipeline like this, probably can not detect the pipe temperature of the whole periphery of pipeline exactly by using 1 the 2nd temperature sensor.On this problem, the thermal flowmeter of this optimal morphology comprises a plurality of the 2nd temperature sensors, try to achieve the average tube channel temp of the pipe temperature that has reflected the whole periphery of pipeline well, therefore, the correction that use is tried to achieve rightly according to the average tube channel temp can be removed the influence of external environment condition to flow measurement well.Particularly, the form of the 2nd temperature sensor is set according to the both sides at the perpendicular line of the cross-section center by pipeline, even when direct light is radiated on the part of the pipeline that is exposed to outdoor setting, when making the pipe temperature rising of this part, can try to achieve the average tube channel temp according to pipe section that is subjected to the light-struck part of direct projection and the pipe temperature that is not subjected to the part of illumination, and use and the corresponding correction of this average tube channel temp, can remove the influence of sunshine to flow measurement.
Description of drawings
Fig. 1 is the synoptic diagram of the thermal flowmeter of one embodiment of the present invention.
Fig. 2 is registered in the temperature difference correction chart that thermal flowmeter shown in Figure 1 has for the temperature difference correction, with the example of the correction curve map of the corresponding per unit temperature difference of gas flow rate.
Fig. 3 is expression improves the result of flow measurement precision by the temperature difference correction a curve map.
Fig. 4 is the process flow diagram of the flow measurement order of expression thermal flowmeter shown in Figure 1.
Fig. 5 is the synoptic diagram that constitutes the vane of thermal flow rate sensor.
Fig. 6 is the summary sectional view of expression toward piping erection thermal flowmeter structure.
Fig. 7 expression is along with the rising of outer temperature degree produces, the heating temp of heating element is with respect to the synoptic diagram of the deviation of the heating temp of regulation.
Embodiment
Below, with reference to the thermal flowmeter of description of drawings an embodiment of the invention.
The thermal flowmeter of present embodiment constitutes the gas meter, flow meter that flows through the gas flow in the fluid passage that is formed by pipeline as measurement.As shown in Figure 1, gas meter, flow meter comprises a plurality of for example 4 thermal flow rate sensor 11a, 11b, 11c, 11d on the outer wall that is arranged on pipeline 10, that expression is flow through that the output of the gas flow rate (more generally being exactly rate of flow of fluid) in the pipeline 10 sends respectively; Be used to detect the 1st temperature sensor 12a of fuel gas temperature; Be used to detect the 2nd temperature sensor 12b, the 12c of the temperature of pipeline 10; And the pressure transducer 13 that is used to detect gaseous-pressure.
Be exactly that each thermal flow rate sensor 11a～11d has the structure identical with vane shown in Figure 51 basically in more detail.That is, each flow sensor has the 1st and the 2nd detector unit Ru, the Rd that crosses setting separated from each other on the direction F at gas-flow; And be arranged on heating element Rh between two temperatures detecting element Ru, the Rd.And, the 1st above-mentioned temperature sensor 12a is set, to replace the detector unit Rr of Fig. 5.Also have, also detector unit Rr can be used with the 1st temperature sensor 12a.
The heating element Rh of flow sensor 11a, 11b and flow sensor 11c, 11d is different with distance between detector unit Ru, the Rd, has different fluid-velocity survey accumulator mutually.For example, flow sensor 11a, 11b constitute the low-speed flow quantity sensor that detects usefulness as low flow volume region, flow sensor 11c, 11d constitute the high velocity stream quantity sensor that detects usefulness as high flow volume region, according to open the described gas flow of 2003-121232 communique as the spy, correspondingly select to use low-speed flow quantity sensor 11a, 11b or high velocity stream quantity sensor 11c, 11d.And flow sensor 11a～11d is separately positioned on 4 positions altogether of upper left side, upper right side, lower-left side and the lower right side of the cylindric outer wall of pipeline 10 with 90 ° interval along peripheral direction.
In addition, the 1st temperature sensor 12a is made of (thermistor) such as thermistors, and its temperature detection end is configured in the central portion in the pipeline 10, to detect the fuel gas temperature of pipeline central portion.Have, the 2nd temperature sensor 12b, 12c are separately positioned on the both sides of the perpendicular line that passes through cross-section of pipeline center outer wall, for example outer peripheral face of pipeline 10 again, preferably be arranged on high velocity stream quantity sensor 11c, 11d near.
In having the gas meter, flow meter of said structure (thermal flowmeter), each flow sensor 11a～11d is contained in the pipeline 10 of packing on the wiring board with the resistance value difference of the driving circuit of heating element Rh and detected temperatures detecting element Ru, the Rd bridge diagram as temperature difference.
These flow sensors 11a～11d links to each other with the gas meter, flow meter measurement section 20 that with CPU is main formation through cable 16 with the interface portion of installing on the selection circuit substrate 14 of the periphery wall that is installed on pipeline 10, makes this sensor output (detection signal) to measurement section 20 outputs.And the 1st links to each other with measurement section 20 with the 2nd temperature sensor 12a～12c and the pressure transducer 13 also interface portion through selecting circuit substrate 14.
The characteristics of measurement section 20 are, comprise the function (temperature difference correcting device) of carrying out the temperature difference correction, this function is according to passing through the poor of the 1st temperature sensor 12a fuel gas temperature that detects and the pipe temperature that detects by the 2nd temperature sensor 12b, 12c, reference temperature(TR) difference correction chart 24 carries out the temperature difference correction to the detection signal from flow sensor 11a～11d.
The difference of the output of the 1st and the 2nd detector unit during as mentioned above, each flow sensor 11a～11d drives heating element is sent as detecting output.The detection output of the flow sensor when identical with fuel gas temperature with respect to the pipe temperature that does not have external environment influence (below, as benchmaring output), the detection output of flow sensor correspondingly changes according to the influence degree (extent of fuel gas temperature and pipe temperature) of external environment condition.Below, the difference of fuel gas temperature and pipe temperature is called temperature difference, and, the variation of the detection output of flow sensor is called the output variation of flow sensor.
Like this, the detection of flow sensor output changes along with temperature difference.In other words, the output variation of flow sensor can be represented as the function of temperature difference.And the output variation of flow sensor also changes with gas flow rate (gas flow) as described later in detail.
In the gas meter, flow meter of present embodiment, attempting by offsetting the output variation of flow sensor with big or small identical and correction opposite in sign of using such output variation, is that the flow sensor of the per unit temperature difference that will represent as the function of temperature difference and gas flow rate is exported correction and is registered in the temperature difference correction chart 24 basically.
In order to ask for such correction, present inventors at first ask for the relation of the output variation of temperature difference and gas flow rate and flow sensor by following experiment.
As shown in Figure 1, the test unit of flow sensor of will packing in pipeline is arranged in the calibration cell, make the combustion gas of known temperature flow through in the pipeline of experimental provision with known flow velocity, make the interior temperature (corresponding) of calibration cell identical simultaneously with fuel gas temperature with pipe temperature, under this state, the detection output of measured discharge sensor is to ask for benchmaring output.Then, one side changes gas flow rate, and one side is asked for the benchmaring output of various gas flow rates.Then, temperature remains under the state than the high uniform temperature of fuel gas temperature in calibration cell, surveys the detection output of the flow sensor of various gas flow rates.And then, with temperature one side in the calibration cell adding general orientation or reducing direction and change the detection output of a measured discharge sensor towards fuel gas temperature.Then, the actual measurement of the flow sensor of temperature and each gas flow rate detects and to deduct benchmaring output corresponding with it output in each calibration cell, to ask for the output variation of the flow sensor of temperature and gas flow rate in the various calibration cells.
And then, detect output data and benchmaring output data according to above-mentioned actual measurement, present inventors are for all temps difference and various gas flow rate, ask for the output change ratio (%/℃) of the flow sensor of per unit temperature difference, its result, for each temperature difference, obtain representing gas flow rate and per unit temperature difference sensor output change ratio relation family curve (with one of them with the dotted line of Fig. 2 and put on label A and represent).
The family curve A that dots in Fig. 2 represents that the output change ratio of the flow sensor of per unit temperature changes along with the variation of gas flow rate.Too, the output change ratio and the temperature difference of the flow sensor of this expression per unit temperature difference are irrelevant, are roughly constant for other temperature difference for such tendency.
That is, the output variation of the flow sensor that produces because of the difference of fluid temperature (F.T.) and pipe temperature depends primarily on gas flow rate (more generally being exactly rate of flow of fluid) and changes this fact and obtained confirmation.And though the output variation also changes along with the variation of temperature difference, if gas flow rate is identical, then the output of per unit temperature difference change ratio has nothing to do with temperature difference, is roughly constantly, and this fact also can be confirmed.
According to above-mentioned understanding, in the gas meter, flow meter of present embodiment, tackling the output change of the flow sensor 11 that produces in poor (more generally being exactly the influence of external environment condition) because of fluid temperature (F.T.) and pipe temperature revises, will be representing with B with respect to the family curve of transverse axis and family curve A symmetry among Fig. 2, be registered in the temperature difference correction chart 24 with the flow sensor output correction (more generally being exactly the flow correction amount of per unit temperature difference) of the corresponding per unit temperature difference of gas flow rate.
Then, from temperature difference correction chart 24, ask for difference and the corresponding correction of gas flow rate with fuel gas temperature and pipe temperature, use this correction that the temperature difference correction is carried out in the output (more generally being exactly gas flow) of flow sensor 11.
Specifically be exactly, the gas flow rate of representing according to the output of flow sensor 11, from temperature difference correction chart 24, correspondingly ask for the correction of per unit temperature difference, detect fuel gas temperature by the 1st temperature sensor 12a on the other hand, simultaneously by the 2nd temperature sensor 12b, 12c detector tube channel temp.Then, multiply each other by difference correction and fuel gas temperature and pipe temperature, to ask for for the required flow correction amount of this temperature difference, by with this flow correction amount and the gas flow addition that detects by flow sensor 11, carry out the temperature difference correction to detecting gas flow, can ask for the combustion gas actual flow that flows through pipeline 10 accurately.
The effect of the reduction measuring error that obtains by above-mentioned temperature difference correction can be confirmed from measurement characteristics line a, the d of the relation of expression gas flow rate shown in Figure 3 and measuring error.Among the figure, measurement characteristics line d is that resulting actual measurement detects output and benchmaring output and measures gas flow and generate according to each gas flow rate when in the experiment of the experimental provision stated in the use temperature in the calibration cell being decided to be-25 ℃, and the measuring error shown in the longitudinal axis of Fig. 3 (%) is actual measurement to be detected that output is exported divided by benchmaring with the difference of benchmaring output and 100 times of the result that obtains.In addition, output applies the revised actual measurement detection output of above-mentioned temperature difference to the measuring error among the measurement characteristics line a and benchmaring output is asked for according to detecting for actual measurement.Measurement characteristics line d represents that the measurement gas flow that does not apply the temperature difference correction contains very big error, and measurement characteristics line a represents that the error of the revised measurement gas flow of temperature difference is below 1%.Measurement characteristics line b, c among Fig. 3 applies result that temperature difference correction obtain to measuring gas flow when temperature in the calibration cell when being 40 ℃ and 60 ℃, expression can fully be suppressed to measuring error below 1% by the temperature difference correction, can access sufficiently high measuring accuracy.
Apparent according to the above description, among the present invention, the external environment condition that vane 1 by 10 pairs of formation flow sensors of pipeline works, in fact for the influence degree of the flow measurement of flowing through the fluid on the flow sensor, can utilize the difference of fluid temperature (F.T.) that detects by the 1st temperature sensor 12a and the pipe temperature that detects by the 2nd temperature sensor 12b, 12c to obtain simply.And then, using the correction of correspondingly asking for according to this temperature difference, with the fluid flow of modified flow rate sensor, therefore, can revise effectively simply measuring flow, can improve measuring accuracy.
About the correction of said temperature difference, specifically carry out flow measurement processing sequence shown in Figure 4 and carried out by flow operational part 21.In this flow measurement is handled, for the correction of each output of flow sensor 11a～11d or the flow rate calculation of carrying out according to revised sensor output, with each flow sensor is that unit carries out, in the following description, use with reference to label 11 and represent each flow sensor.
In flow measurement is handled, at first, will import [step S1] from the sensor of flow sensor 11.Then, to revising [step S2] according to the sensor output of sensitivity that combustion gas kind (more general is exactly the kind of fluid) correspondingly adjusts the detection of flow sensor.And then, according to the gaseous-pressure that detects by pressure transducer 13, with reference to pressure correction table 23, pressure correction [step S3] is correspondingly carried out in output to sensor, according to the fuel gas temperature that detects by the 1st temperature sensor 12a, reference temperature(TR) correction chart 22 is to sensor output correspondingly carrying out temperature correction [step S4].Like this, after the variation of depending on combustion gas kind, gaseous-pressure and fuel gas temperature of the detection characteristic of flow sensor 11 is revised respectively, benchmaring characteristic according to flow sensor 11, individual difference to each fluid sensor is correspondingly revised [step S5], according to the sensor output that has applied these corrections, ask for the gas flow rate (gas flow) [step S6] in the pipeline 10.
Also have, the gas flow rate computing that output is carried out according to the correction sensor among sensor output correcting process among step S1～S5 and the step S6, can carry out simultaneously for 4 flow sensor 11a～11d, perhaps also can the sensor output of flow sensor 11a～11d be imported so that assigned frequency is simultaneously touring through selecting wiring board 14, one side is carried out with the method for timesharing.
In the flow measurement of Fig. 4 is handled, the gas flow rate asked for respectively according to the sensor output of flow sensor 11a～11d like this is in addition average, in the hope of being averaged gas flow rate [step S7].Then, according to this average gas flow rate and poor by the 1st temperature sensor 12a fuel gas temperature that detects and the pipe temperature that detects by the 2nd temperature sensor 12b, 12c, reference temperature(TR) difference correction chart 24, ask for the correction of per unit temperature difference, itself and temperature difference are multiplied each other, ask for the flow correction amount.On the other hand, one side drives heating element Rh, and one side is according to the output difference measurements gas flow of the 1st and the 2nd detector unit Ru, Rd.Then, the use traffic correction is carried out temperature difference correction [step S8] to measuring gas flow, and the revised gas flow of this temperature difference is exported [step S9] as the gas flow from thermal flowmeter.After, by carrying out above-mentioned processing repeatedly, proceed gas flow and measure.
Like this according to having an as above thermal flowmeter of structure, modifying factor applies the flow measurement error of the flow sensor 11 that the effect of heat produces to thermal flow rate sensor 11 from the outside by pipeline 10 simply.And the 1st temperature sensor 12a by being installed in pipeline 10 and the 2nd temperature sensor 12b, 12c detect the temperature difference of pipeline 10 and fluid, by carry out the so simple means of temperature difference correction according to this temperature difference, can remove the flow measurement error.
In the above-described embodiment, be will be average in addition by the pipe temperature that 2 the 2nd temperature sensor 12b, 12c measure respectively, to detect the pipeline medial temperature, thus, even only impinge upon a side of pipeline 10 for example and make and also can correctly estimate pipe temperature under the situation that the temperature of a side rises at sunshine.And, as mentioned above, since with the 2nd temperature sensor 12b, 12c be arranged on high velocity stream quantity sensor 11c, 11d near, even therefore using low-speed flow quantity sensor 11a, 11b to carry out under the situation of flow measurement, can not be subjected to heat affecting, exactly the detector tube channel temp from low-speed flow quantity sensor 11a, 11b yet.Also have,,, therefore can not be subjected to heat affecting basically from high velocity stream quantity sensor 11b, 11c because flow velocity itself is very fast using high velocity stream quantity sensor 11b, 11c to carry out under the situation of flow measurement, and detector tube channel temp exactly.Therefore, near the 2nd temperature sensor 12b, 12c that can be by being arranged on high velocity stream quantity sensor 11c, 11d be the detector tube channel temp exactly, carries out above-mentioned temperature difference correction simultaneously effectively.
And, owing to, compare, can simplify the structure of temperature difference correction chart 24 with the correction of situation all will register to(for) each temperature difference as long as the correction of per unit temperature difference is registered in the temperature difference correction chart 24 just passable.And, as long as to ask for the flow correction amount just passable owing to will multiply each other according to the correction that detects the per unit temperature difference that gas flow asks for from temperature difference correction chart 24 and temperature difference (fuel gas temperature and pipe temperature poor), therefore not only to the calculating of flow correction but also to the temperature difference correction, all do not want complicated processing, can carry out simply.
Also have, the present invention is not only limited to above-mentioned embodiment.
For example, in embodiment, the gas meter, flow meter that comprises 2 low-speed flow quantity sensors and 2 high velocity stream quantity sensors has been described, but the present invention also can be applied to measure the thermal flowmeter of combustion gas fluid flow in addition, and, the quantity of flow sensor does not have special restriction yet, not necessarily needs to comprise two kinds of sensors of low-speed flow quantity sensor and high velocity stream quantity sensor yet.And the quantity of the 1st and the 2nd temperature sensor does not have special restriction yet.In addition, as long as in the scope that does not break away from main points of the present invention, can carry out various distortion and enforcement.
Claims (7)
1. a thermal flowmeter is characterized in that having
Be installed in the ducted thermal flow rate sensor that fluid flows through, described thermal flow rate sensor is included on the flow direction the 1st and the 2nd detector unit across heating element setting separated from each other;
The 1st temperature sensor of the fluid temperature (F.T.) in the described pipeline is flow through in detection;
Detect the 2nd temperature sensor of described pipe temperature;
The temperature that detects respectively according to the 1st and the 2nd detector unit of described thermal flow rate sensor is asked for the flow measurement device of fluid flow; And
The temperature difference correcting device that the fluid flow of described flow measurement device being asked for based on the output change characteristic of the described thermal flow rate sensor poor, that cause according to temperature difference of the fluid temperature (F.T.) that detects by described the 1st temperature sensor and the pipe temperature that detects by described the 2nd temperature sensor is revised.
2. thermal flowmeter as claimed in claim 1 is characterized in that,
Described temperature difference correcting device comprises the temperature difference correction chart that the output variation corresponding to the described thermal flow rate sensor of the difference of fluid temperature (F.T.) and pipe temperature is write down as the change characteristic corresponding to described fluid flow difference,
Fluid temperature (F.T.) and the difference of pipe temperature and the fluid flow that detects by described thermal flow rate sensor that described temperature difference correcting device detects respectively according to the described the 1st and the 2nd temperature sensor, from described temperature difference correction chart, ask for described output variation, and will export variation as correction to described fluid flow.
3. hot type meter as claimed in claim 1 is characterized in that,
Described temperature difference correcting device comprises the temperature difference correction chart that the flow correction amount of per unit temperature difference is represented as the function of the difference of fluid temperature (F.T.) and pipe temperature and fluid flow, according to the fluid temperature (F.T.) that detects by described the 1st temperature sensor, pipe temperature by described the 2nd temperature sensor detection, and measure fluid flow by the temperature that the described the 1st and the 2nd detector unit detects, from described temperature difference correction chart, ask for the flow correction amount of per unit temperature difference according to the fluid flow of this measurement
To multiply each other with the difference of the pipe temperature that detects by described the 2nd temperature sensor and the flow correction amount of described per unit temperature difference by the fluid temperature (F.T.) that described the 1st temperature sensor detects, ask for described flow correction amount.
4. thermal flowmeter as claimed in claim 1 is characterized in that,
Described the 1st temperature sensor detects the fluid temperature (F.T.) of the central portion in the described pipeline.
5. thermal flowmeter as claimed in claim 1 is characterized in that,
Described the 2nd temperature sensor detects the wall surface temperature of described pipeline.
6. thermal flowmeter as claimed in claim 1 is characterized in that,
A plurality of described the 2nd temperature sensor of setting separated from each other on the peripheral direction of described pipeline,
The mean value of the temperature that will detect respectively by described a plurality of the 2nd temperature sensors is asked for as described pipe temperature.
7. thermal flowmeter as claimed in claim 6 is characterized in that,
Symmetria bilateralis at the perpendicular line of the cross-section center by described pipeline is provided with a plurality of described the 2nd temperature sensors.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP251050/2002 | 2002-08-29 | ||
| JP2002251050A JP4355792B2 (en) | 2002-08-29 | 2002-08-29 | Thermal flow meter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1678889A CN1678889A (en) | 2005-10-05 |
| CN100350223C true CN100350223C (en) | 2007-11-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB038204169A Expired - Lifetime CN100350223C (en) | 2002-08-29 | 2003-08-29 | Thermal flowmeter |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JP4355792B2 (en) |
| CN (1) | CN100350223C (en) |
| AU (1) | AU2003257603A1 (en) |
| DE (1) | DE10393185B4 (en) |
| WO (1) | WO2004020958A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103674136A (en) * | 2012-09-17 | 2014-03-26 | 东京计装株式会社 | Thermal flowmeter |
| CN110763278A (en) * | 2019-11-14 | 2020-02-07 | 上海权宥环保科技有限公司 | Measuring method for measuring fluid medium parameters in pipeline |
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| DE102005057688A1 (en) * | 2005-12-01 | 2007-06-14 | Endress + Hauser Flowtec Ag | Device for determining and / or monitoring the mass flow rate of a gaseous medium |
| CN101430216B (en) * | 2007-11-05 | 2015-11-25 | 北京七星华创电子股份有限公司 | Mass flow sensor and control system and realize the method that mass rate controls |
| DE102007062908A1 (en) | 2007-12-21 | 2009-06-25 | Endress + Hauser Flowtec Ag | Process variable e.g. concentration, determining method for biogas, involves measuring volume flow rate of flowing medium by using measuring principles, and determining process variable from measured values of measuring principles |
| US8438936B2 (en) * | 2011-06-03 | 2013-05-14 | General Electric Company | Sensor assembly including a collar for mounting sensors to a pipeline |
| DE102012102094A1 (en) * | 2012-03-13 | 2013-09-19 | Pierburg Gmbh | Device for determining a gas mass flow and method for recalibrating such a device |
| JP6010440B2 (en) * | 2012-12-03 | 2016-10-19 | アズビル株式会社 | Flow sensor |
| US9612146B2 (en) | 2014-02-07 | 2017-04-04 | Honeywell International, Inc. | Airflow sensor with dust reduction |
| GB2533936B (en) | 2015-01-07 | 2017-10-25 | Homeserve Plc | Flow detection device |
| GB201501935D0 (en) | 2015-02-05 | 2015-03-25 | Tooms Moore Consulting Ltd And Trow Consulting Ltd | Water flow analysis |
| CN107421858A (en) * | 2017-06-15 | 2017-12-01 | 中国科学技术大学 | Portable type electronic product and its microparticle thing sensing device |
| JP2019035640A (en) * | 2017-08-14 | 2019-03-07 | アズビル株式会社 | Thermal flow meter |
| DE102018105046B4 (en) | 2018-03-06 | 2023-05-04 | Endress+Hauser Flowtec Ag | Thermal flow meter |
| JP7067789B2 (en) * | 2018-07-02 | 2022-05-16 | サーパス工業株式会社 | How to determine the thermal flowmeter and its weighting factor |
| EP3637218A1 (en) * | 2018-10-10 | 2020-04-15 | Gambro Lundia AB | Fluid warming device for an extracorporeal blood treatment apparatus and method for detecting a fluid temperature at an outlet of a fluid warming device for an extracorporeal blood treatment apparatus |
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| CN110763278A (en) * | 2019-11-14 | 2020-02-07 | 上海权宥环保科技有限公司 | Measuring method for measuring fluid medium parameters in pipeline |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4355792B2 (en) | 2009-11-04 |
| CN1678889A (en) | 2005-10-05 |
| DE10393185B4 (en) | 2013-01-31 |
| AU2003257603A1 (en) | 2004-03-19 |
| DE10393185T5 (en) | 2005-10-20 |
| JP2004093180A (en) | 2004-03-25 |
| AU2003257603A8 (en) | 2004-03-19 |
| WO2004020958A1 (en) | 2004-03-11 |
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