DE19517236A1 - Monitoring flow of flowing medium using at least one heating element - Google Patents

Monitoring flow of flowing medium using at least one heating element

Info

Publication number
DE19517236A1
DE19517236A1 DE1995117236 DE19517236A DE19517236A1 DE 19517236 A1 DE19517236 A1 DE 19517236A1 DE 1995117236 DE1995117236 DE 1995117236 DE 19517236 A DE19517236 A DE 19517236A DE 19517236 A1 DE19517236 A1 DE 19517236A1
Authority
DE
Germany
Prior art keywords
temperature
flowing medium
heating element
unaffected
semiconductor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
DE1995117236
Other languages
German (de)
Other versions
DE19517236C2 (en
Inventor
Walter Dipl Ing Reichart
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
IFM Electronic GmbH
Original Assignee
IFM Electronic GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by IFM Electronic GmbH filed Critical IFM Electronic GmbH
Priority to DE1995117236 priority Critical patent/DE19517236C2/en
Publication of DE19517236A1 publication Critical patent/DE19517236A1/en
Application granted granted Critical
Publication of DE19517236C2 publication Critical patent/DE19517236C2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/684Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/69Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/684Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/696Circuits therefor, e.g. constant-current flow meters
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/696Circuits therefor, e.g. constant-current flow meters
    • G01F1/698Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
    • G01F1/6986Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters with pulsed heating, e.g. dynamic methods

Abstract

The temp. of the temp. measuring is determined from at least one voltage difference of two transmission voltages, having different transmission currents at the same temp. A compensation for the influencing of the connection between the flow speed of the flowing medium and the temp. difference, by the temp. of the flowing medium uninfluenced by the heating element, is taken. This is based on a control of the transmission of the semiconductor junction (5), depending on the temp. of the flowing medium uninfluenced by the heating element.

Description

The invention relates to a method for monitoring the flow of flowing Me serve, with the help of at least one partially influencing the flowing medium Heating element, with the help of at least one at least predominantly from the Heating element unaffected portion of the flowing medium affected first Temperaturmeßelementes and with the help of at least one at least predominantly from affected by the heating element proportion of the flowing medium second temperature measuring element, in which depending on the temperature differences boundary between the first and the second temperature measuring element one of the currents flow rate of the flowing medium proportional measurement signal generated becomes. The invention further relates to a device for realizing the invention method according to the invention. For this, reference is made to the preamble of the patent claim 5.

Flow meters of the type in question, in particular calorimetric working flow monitors have long been and in many embodiments knows (see e.g. German Offenlegungsschriften 24 47 617, 26 29 051, 32 13 902, 32 22 046, 37 13 981, 38 11 728, 38 25 059, 39 11 008, 39 43 437 and 44 06 541). In the known calorimetric currents on which the invention is based the difference between the temperatures of a heat flowed boundary layer of the flowing medium to the temperature of the unaffected flowing medium evaluated to the speed of the flowing To determine the medium. The temperature difference described is proportional to the heat transfer coefficient α. The heat transfer coefficient α is again around a function of the speed of the flowing medium and the tempera ture of the portion of the flowing medium unaffected by the heating element. At the methods known from the prior art for monitoring the currents With flowing media, it is often assumed that the influence of temperature the proportion of the flowing medium which is not influenced by the heating element will, d. H. the temperature of the flowing medium in front of the flow switch is neglected, i.e. the heat transfer coefficient α and thus the measured Temperature difference directly proportional to the flow speed of the flow the medium is.  

Cause of the described simplification of the influences on the heat transfer co Efficient and thus the measured temperature difference is the structure of the previously known flow switch. In general, the measurements of tempera difference made on the basis of bridge circuits in which PTC's, NTC's or other temperature-dependent components used as temperature measuring elements will. With almost all temperature-dependent components it is problematic that this have a non-linear characteristic, which also goes from component to component scatters. On the one hand, this leads to a limited interchangeability of these components, e.g. B. as part of maintenance work, on the other hand to difficulties in construction of a precisely working flow switch. In particular, the known construction parts problematic in that their non-linearity and component dispersion a correction of the dependence of the heat transfer coefficient and thus the measured temperature difference from the temperature of the unbe by heating element influenced portion of the flowing medium is almost impossible.

The lack of a possibility of compensating for the dependence of the heat transfer coefficient or the measured temperature difference on the temperature of the portion of the flowing medium unaffected by the heating element is more or less serious depending on the flowing medium actually monitored. In Fig. 1 of the drawing, the heat transfer coefficient α is shown depending on the speed of the flowing medium at temperatures of 10, 25 and 80 ° C for water. One can clearly see the great dependency of the heat transfer coefficient α on the temperature of the portion of the flowing medium uninfluenced by the heating element, and secondly the non-linearity of this dependency. It is therefore only possible to use one of the known flow monitors for water without errors if the temperature of the portion of the flowing medium uninfluenced by the heating element is known.

In addition to the known temperature-dependent components described so far generally known as a temperature meter, so-called dynamic temperature meter, who work according to the proportional to absolute temperature (PTAT) method (cf. Elektor 1/93, Ing. Harro Kühne, "Dynamic Temperature Meter", pages 54 to 58). These dynamic temperature meters work on the physical principle that the difference in voltage drop across a semiconductor junction at two below  different pass currents directly the product of a constant, the solute temperature and the natural logarithm of the quotient or the ver ratio of the forward currents corresponds. Expressed mathematically, this is physical principle:

The dynamic temperature meters work in such a way that a semiconductor junction is alternately acted upon with two different forward currents. Older known methods use the described physical principle in that that two identically constructed semiconductor junctions, which are on the same tempe rature are subjected to different forward currents. The be Known dynamic temperature meters are characterized by the fact that they have a rela tiv large measurement signal that no adjustment is necessary that the voltage diff reference is directly proportional to the absolute temperature and that the sensor elements are interchangeable without adjustment.

The invention is based on the object, the known methods and ago directions for monitoring the flow of flowing media ten that the measuring accuracy even with varying temperatures of the heating ment unaffected portion of the flowing medium is significantly increased.

In the method according to the invention, the previously shown and explained is Auf surrendered by at least one half lead as the temperature measuring element terübergang is used that the semiconductor transition for temperature measurement with in each case at least a certain forward current is applied that the tem temperature of the temperature measuring element from at least one voltage difference two forward voltages at different forward currents on the same Temperature semiconductor transitions is determined and that a Kompensa tion of influencing the relationship between the flow rate speed of the flowing medium and the temperature difference due to the heating Element unaffected temperature of the flowing medium using a control the forward currents of the semiconductor junctions depending on that of the heating element  unaffected temperature of the flowing medium is made. Erfin Accordingly, it has been recognized that so-called dynamic temperature knives not only because of their generally known properties especially for use as temperature measuring elements in a method for monitoring the Flow of flowing media are suitable, but also have properties They are irrelevant for general use, but they are especially important for Make use particularly suitable in such a process. The fiction depend on the proposed control of the forward currents of the semiconductor junctions gig of the temperature of the flowing medium unaffected by the heating element This is particularly advantageous since the compensation of the influence achieved thereby solution of the relationship between the flow velocity of the flowing Medium and the temperature difference by the unaffected by the heating element Temperature of the flowing medium with high reproducibility and precision is guaranteed.

The previously shown and set out task is in front of the invention direction solved by the features of the characterizing part of claim 5. With Such a device designed according to the invention are all advantages of the inventive method realized.

The Ver according to the invention experiences a first particularly advantageous embodiment drive in that the compensation based on a linear or non-linear Control of the ratio of the forward currents of at least one temperature measurement elements depending on the temperature of the current unaffected by the heating element medium is made. By direct control of the Ver Ratio of the forward currents of one of the two temperature measuring elements is therefore the Sensitivity of this temperature measuring element depending on the temperature of the controlled by the heating element unaffected flowing medium. So it is ge ensures that the measurement signal generated by the inventive method un depending on the temperature of the flowing Me unaffected by the heating element diums is. Whether the control is linear or non-linear depends on the combination hang between the heat transfer coefficient and the temperature of the not of the flowing medium not influenced by the heating element.  

The Ver according to the invention experiences a further particularly advantageous embodiment drive in that as a temperature measuring element with in certain time intervals different pass currents applied semiconductor transition becomes. This measure ensures a particularly simple construction of the temperature measuring element, since in this case only one semiconductor per temperature measuring element gear is necessary.

Finally, the method according to the invention is particularly advantageous design in connection with the last described measure in that the Offset error of a amplifying the output signals of the temperature measuring elements Differential amplifier is suppressed with the help of a chopper network. The one Chopper network is possible because the temperature difference is a difference the signals of the two temperature measuring elements is present as a dynamic signal. Through the measure described, the measuring accuracy of the Ver driving to monitor the flow of flowing media further increased.

In detail, there are now a variety of ways to Ver the invention drive and the device for monitoring the flow stream designing and developing media. On the one hand, reference is made to this the claims 2 to 4 subordinate to claim 1, on the other hand the description of a preferred embodiment in connection with the Drawing. In the drawing shows

Fig. 2 is a block diagram of an embodiment of a circuit for implementing the method according to the invention,

Fig. 3 is a schematic representation of a semiconductor junction to Erläute tion of the underlying physical principle of temperature measurement,

Fig. 4 is a circuit diagram of a sensor bridge for realizing the temperature difference measurement and

Fig. 5 is a circuit diagram of the sensor bridge shown in Fig. 4 in connection with a chopper network downstream of a differential amplifier.

Fig. 2 of the drawing is a block diagram showing an embodiment of a circuit for implementing the method according to the invention. In this example, a sensor system 1 for determining the temperature difference is shown, an evaluation electronics 2 for evaluating the temperature difference supplied by the sensor system 1 , a control electronics 3 controlling the compensation, and an output stage 4 serving to amplify the output signal of the evaluation electronics 2 . As already described in the introduction, the compensation measures carried out by the control electronics 3 have an effect on the sensor system 1 via the evaluation electronics 2 , namely on the ratios of the forward currents alternately applied to a semiconductor junction for certain periods of time.

The semiconductor junction 5 shown schematically in Fig. 3 is in the method according to the Invention, as known for dynamic temperature meters, polarized in forward direction, the forward currents I₁ / I₂ periodically taking different values. The difference between the voltage drops U pn determined for the different forward currents I 1 / I 2 at the semiconductor junction 5 is directly proportional to the absolute temperature of the semiconductor junction 5 .

In Fig. 4 of the drawings a circuit diagram of a sensor bridge is shown, the medium flowing proportional temperature difference is determined with the aid of which the flow speed. In the sensor bridge shown, he temperature measuring element 6 consists of a reference semiconductor junction 7 and a switched reference constant current source 8 . Analogously, the second temperature measuring element 9 consists of a sensor semiconductor transition 10 and a likewise switched sensor constant current source 11 . In the circuit diagram of a sensor bridge shown in Fig. 4, the series resistors are switched synchronously and thus forced under different forward currents for the semiconductor junctions. The accuracy of the ratios of the forward currents can be set very precisely via the resistors arranged in the constant current sources 9 , 11 . Not shown in FIG. 4 is the possibility of controlling the ratios of the forward currents of one of the temperature measuring elements 6 , 9 depending on the temperature of the flowing medium unaffected by the heating element. This can be ensured, for example, by arranging additional switchable resistors in the constant current sources.

In Fig. 5 of the drawing, the sensor bridge shown in Fig. 4 is finally shown with egg nem downstream differential amplifier 12 and an associated chopper network 13 .

Claims (5)

1. A method for monitoring the flow of flowing media, with the aid of at least at least one heating element partially influencing the flowing medium, with the help of at least one at least predominantly influenced by the heating element unaffected portion of the flowing medium first temperature measuring element and with the help of at least one at least predominantly by the Heating element be influenced portion of the flowing medium influenced second Temperaturmeßele mentes, in which depending on the temperature difference between the first and the second temperature measuring element a measuring signal proportional to the flow velocity of the flowing medium is generated, characterized in that at least one semiconductor transition is used as the temperature measuring element, that the semiconductor transition for temperature measurement is acted upon with at least one egg nem specific forward current that the temperature of the tempera ture measuring element from at least at least a voltage difference between two forward voltages at different forward currents at the same temperature is determined semiconductor transitions and that a compensation of the influence of the relationship between the flow velocity of the flowing medium and the temperature difference by the unaffected by the heating element temperature of the flowing medium by controlling the forward currents Semiconductor transitions depending on the temperature of the flowing medium unaffected by the heating element.
2. The method according to claim 1, characterized in that the compensation a linear or non-linear control of the ratio of the passage currents at least one temperature measuring element depending on the heating element unaffected temperature of the flowing medium is made.
3. The method according to any one of claims 1 or 2, characterized in that as Temperature measuring element in certain time intervals with different Passing currents applied semiconductor transition is used.  
4. The method according to claim 3, characterized in that the offset error the output signals of the temperature measuring elements amplifying differential amplifier is suppressed with the help of a chopper network.
5.Device for monitoring the flow of flowing media for processing a method according to one of claims 1 to 4, with a heating element which partially influences the flowing medium, with an at least predominantly influenced by the heating element unaffected by the proportion of the flowing medium influenced first temperature measuring element ( 6 ) and with an at least predominantly influenced by the heating element proportion of the flowing medium second temperature measuring element ( 9 ), wherein depending on the temperature difference between the first and the second temperature measuring element ( 6 , 9 ) a measurement signal proportional to the flow rate of the flowing medium can be generated is characterized in that the temperature measuring element ( 6 , 9 ) each has at least one semiconductor junction ( 7 , 10 ), that the semiconductor junction ( 7 , 10 ) for temperature measurement with at least one specific forward current can be added is that the temperature of the temperature element ( 6 , 9 ) from at least egg ner voltage difference between two forward voltages at different passage currents at the same temperature semiconductor transitions is determinable and that compensation for influencing the relationship between the flow rate of the flowing medium and the temperature difference by the the heating element unaffected temperature of the flowing medium by means of a control of the forward currents of the semiconductor junctions depending on the unaffected by the heating element temperature of the flowing medium is carried out.
DE1995117236 1995-05-15 1995-05-15 Method and device for monitoring the flow of flowing media Expired - Fee Related DE19517236C2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE1995117236 DE19517236C2 (en) 1995-05-15 1995-05-15 Method and device for monitoring the flow of flowing media

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1995117236 DE19517236C2 (en) 1995-05-15 1995-05-15 Method and device for monitoring the flow of flowing media

Publications (2)

Publication Number Publication Date
DE19517236A1 true DE19517236A1 (en) 1996-11-21
DE19517236C2 DE19517236C2 (en) 1998-12-24

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Family Applications (1)

Application Number Title Priority Date Filing Date
DE1995117236 Expired - Fee Related DE19517236C2 (en) 1995-05-15 1995-05-15 Method and device for monitoring the flow of flowing media

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DE (1) DE19517236C2 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3196679A (en) * 1962-05-22 1965-07-27 Lockheed Aircraft Corp Fluid no-flow detection apparatus
US3968685A (en) * 1973-02-16 1976-07-13 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of National Defence Transistor anemometer
DE3424642A1 (en) * 1983-07-11 1985-01-31 Gen Motors Corp Solid air flow probe
DE3518409A1 (en) * 1984-05-22 1985-11-28 Toshiba Kawasaki Kk Semiconductor flow meter for determining flow amount and direction of a flow medium

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3196679A (en) * 1962-05-22 1965-07-27 Lockheed Aircraft Corp Fluid no-flow detection apparatus
US3968685A (en) * 1973-02-16 1976-07-13 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of National Defence Transistor anemometer
DE3424642A1 (en) * 1983-07-11 1985-01-31 Gen Motors Corp Solid air flow probe
DE3518409A1 (en) * 1984-05-22 1985-11-28 Toshiba Kawasaki Kk Semiconductor flow meter for determining flow amount and direction of a flow medium

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DE-Z: Elektor 1/93, S. 54-58 *

Also Published As

Publication number Publication date
DE19517236C2 (en) 1998-12-24

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OP8 Request for examination as to paragraph 44 patent law
D2 Grant after examination
8363 Opposition against the patent
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8339 Ceased/non-payment of the annual fee