DE102008020874B4 - Flow or vortex sensor - Google Patents

Abstract

A flow or vortex sensor (12) comprising a first hot wire sensor element (10) micromachined on a substrate (20) for measuring a first component of a fluid or vortex field of a fluid,
and at least one second hot wire sensor element (36) micromachined on a substrate (20) disposed at a fixed angle to the first hot wire sensor element (10) to measure at least one second component of the flow or vortex field different from the first component.
characterized,
in that each microfabricated hot wire sensor element (10, 36, 38, 40) has elongated projections (24, 25) or pins projecting from a base body (18) of the substrate (20), between an end region of a first projection (24) and pin a hot wire member (26) is freely suspended from an end portion of a second protrusion (25) which is adapted to be heated by an electric current flowing through the hot wire member (26), and that the first protrusion (24) or first Pin in its longitudinal direction longer than the second projection (25) or ...

Description

The Invention relates to a flow or vortex sensor with a first hot-wire sensor element micromachined on a substrate for measuring a first (directional) component of a flow or Vortex field of a fluid.

Micromachined hot wire sensor elements for flow measurement (hot wire anemometry) are known from US Pat US 5,883,310 , of the US 5,231,878 , of the US 4,884,443 as well as the EP 1 348 937 A2 , as well as the EP 1 031 821 A1 known. For more details on microfabrication techniques of such hot wire sensor elements, reference is expressly made to the aforementioned references.

The Prior art microfabricated hot wire sensor elements are very compact and accurately constructed and serve a mass flow of a Fluids flowing along a predefined direction to measure.

From the WO 03/062758 A1 For example, another microfabricated hot wire sensor element is known in which a hot wire element is stretched between two elongate protrusions that are bent out of a plane of a substrate.

From the US2007 / 0113644 A1 For example, a number of other microfabricated hot wire sensor elements are known. In this case, the production is such that a hot wire element which can be heated by current and temperature detection electrodes are fabricated on a substrate in such a way that they bend out of the surface plane of the substrate during an etching step on account of material stresses.

It is also an embodiment described in which several such Hitzdrahtelemente, each have a triangular shaped hot wire, and several as curved meandering conductor loops formed temperature detection electrodes in a circular arrangement are provided around a center. The multiple temperature electrodes and the several hot wire elements surrounding this center are arranged distributed, can each be contacted via electrode pads. This arrangement forms the preamble of the appended claim 1.

For research and applications in fluid mechanics is however common a monitoring of flow fields desirable, what a vectorial speed (amount and direction) of flow and vortex fields should be measured at least locally. For example is a control, control and influencing of the air flow and in particular of vortices in aerodynamic systems, such as For example, aircraft, in particular aircraft, helicopters or unmanned missiles, a big Challenge to optimize performance, especially with regard to safety aspects, regarding the Minimization of energy consumption or traffic control near from airports. In particular, the formation of eddies and wake turbulence behind an airplane while the take-off and landing at an airport for minimizing the between needed two planes intervals crucial and thus determines the maximum traffic capacity.

The spatial and temporal resolution such local measurements of the vectorial flow velocity and the Vortex fields, this means in particular the size of the measuring volume and the frequency response, are fundamental criteria for selection of suitable measuring techniques.

Other important criteria include the mutual influence of feelers and Flow, that Signal-to-noise ratio and other effects that could affect the measurement quality and the sensor transmission function change could.

Already For several decades, hot wire wind strength measurement or hot wire anemometry has been used (Hot Wire Anemometry, short HWA) for flow measurement especially in turbulent flows, used.

The from the documents mentioned in the prior art known Microfabricated hot wire sensors are compact and robust can be built up but only for simple flow measurements be used.

task The invention is a simple and inexpensive Flow sensor ready to ask, to measure the vectorial velocity and of vertebral fields is suitable.

These Task we by a flow or Eddy probe with the characteristics of the attached Claim 1 solved.

advantageous Embodiments of the invention are the subject of the dependent claims.

Of the has flow or vortex sensor according to the invention in addition to a first micromachined on or on a substrate Hot wire sensor element used to measure a first (directional) component a flow or vortex field of a fluid is suitable and designed, even more a second hot wire sensor element microfabricated on a substrate.

This second hot wire sensor element is in arranged at a fixed angle to the first Hitzdrahttsensorelement and so formed so that at least one of the first (directional) component different second (directional) component of the flow or vortex field can be measured.

With In particular, sensors can be used in this basic principle of the invention and build sensor systems or sensor devices that are capable of the flow vector (Amount and direction) and the turbulence of a flow experimentally - in particular, but not exclusively, also in wind tunnel experiments - too determine and measure.

The The first and the second hot wire sensor elements each have a wire element on, which is heatable by means of an electric current. This Heatable first wire element is hereinafter also referred to as Hitzdrahtelement designated.

To the hanging the Hitzdrahtelemente such that they are free from the measured Flow are flushable, it is envisaged that any microfabricated hot wire sensor element elongated projections has that of a base body protrude from the substrate. Between the free ends of the at least two protruding elongated microfabricated hot wire sensor element protrusions is then a hot wire element freely suspended.

Around in as possible in a simple manner using microfabrication techniques different orientation of the Hitzdrahtelemente adjacent To achieve hot wire sensor elements is further according to the invention provided that a first of these elongated projections formed longer is as a second of these projections, so that the hot-wire element in terms of of the base body aslant suspendable is. A different orientation of two hot wire elements let yourself then just for example by mirror image orientation and Achieve arrangement of the Hitzdrahtsensorelemente.

In a preferred complete Design of a complete sensor system, it is desirable that the flow or vortex sensor information about all three components of the flow vector and all components of the vortex vector at the position of interest supplies. However, there are also applications where a limited number of dimensions for the velocity vector or the vortex vector already sufficient is. The invention proposes Therefore, a new, based on microfabrication flow or Eddy probe with microfabricated hot wire sensor elements for at least two directional components at least one of these vectors. Such a flow or Eddy probe can be manufactured with high accuracy in a cost effective manner.

Under Using microfabrication techniques, very small hot wire sensor elements can be fabricated and be positioned with high accuracy relative to each other. This preserves you have a very high spatial Resolution. The accuracy of the positioning can be with no special effort Microfabrication techniques obtained.

Although Also, a different orientation of the hot wire elements of the first and second hot wire sensor element is possible so receives you get the best efficiency for different measuring two mutually perpendicular field or Vector components when the hot-wire elements are vertical extend to the respective components to be measured. Accordingly, it is preferred that the two hot wire elements of the first and second hot wire sensor element at an angle of about 90 ° to each other extend.

This Angle of 90 ° can be particularly easy to achieve when the hot wire element and one of the two elongated ones Projections, in particular the first, longer Projection, span an angle of about 45 degrees.

A simple microfabrication is achievable if the base body has a flat base plate is. The projections can then prongs or prongs be, preferably from a narrow side of the base plate extend further in the plane of extension of the base plate - in particular as integral extensions the base plate. The hot-wire element can then also be parallel be suspended to the extension plane of the base plate. Thereby let yourself form a particularly flat Hitzdrahtsensorelement.

To the Forming a crosswise arrangement of the hot wire elements of the first and second hot-wire element, such flat structures, for example, in a mirror image arrangement or training flat be packed on top of each other.

Thereby receives to a compact assembly or Hitzdrahtsensoreinheit the flow or vortex sensor for Measurement of two directional components. The flow or vortex sensor can in particular more of these assemblies, at least formed from a first and a second hot wire sensor element, so all Directional components of the velocity vector and the vortex field to eat.

In addition to the first, heatable wire element, one, several or all of the hot wire Sensor elements also have a second or possibly a third wire element, which are heated only indirectly by coming from the heated wire element flow and / or from the ambient temperature. As a result, on the one hand, the ambient temperature can be determined in order to separate the pure flow effects on the temperature of the hot-wire element from the effects of the ambient temperature. On the other hand, flow effects can also be measured. The second and the third wire element are preferably arranged substantially parallel to the Hitzdrahtelement and with an interspaced by the flow or vortex field spacing.

The Temperature of the wire elements leaves Particularly easy to measure that they are to generate an electrical signal are formed, from which the respective Temperature can be determined.

on the other hand can be a signal from a to maintain a specific Temperature necessary electricity can be obtained. Both are special effective for example by an electrical temperature coefficient the electrical resistance of the respective wire element achievable. Z. B. allows then a measurement of the resistance of the wire element a statement of its temperature.

Around To be able to measure the electrical resistance of the wire element accurately and / or essentially only the hot-wire element and non-electrical connection lines through the flowing To heat electricity, it is further preferred that the respective wire elements are connected with an electrical connection whose electrical Resistance is much lower than the electrical resistance of the wire element itself.

A high temperature dependence the electrical resistance of the wire elements can be with certain materials for reach the wire elements. Therefore, the wire elements are preferable of polycrystalline semiconductor material, in particular of polycrystalline Silicon, or a thin one Metal film, in particular of platinum, of a platinum-rhodium alloy, Tungsten or gold.

A particularly simple and accurate relative arrangement of the first and the second Hitzdrahtsensorelementes each other and a simple Production of the flow or vortex sensor is achievable when both the first and second hot wire sensor elements are formed on a common substrate.

If the substrate of the respective hot-wire elements made of semiconductor materials, in particular from monocrystalline semiconductor materials, and here further preferably made of monocrystalline silicon, are formed, let yourself a low thermal time constant and good thermal insulation reach the Mikroheizelements on the substrate. The projections are preferably also formed from the substrate and serve as carrier for flow-sensitive thin film resistors that are used as Hitzdrahtelemente.

A substantial improvement over previous ones flow or vortex sensors can be expected when the technology of microfabrication as a basis for the production of such measuring devices the base of silicon used as the material to be structured becomes. The structures can are then formed lithographically and can by means of advanced thin layer deposits and / or etching technologies and / or Eroding technologies are formed.

By The invention provides an integrated sensor structure which capable of doing so is different components of the velocity and / or vortex vector to measure a fluid flow. This structure may be in MEMS technique (Micro-Electric-Mechanical System Technology) be made. This allows the hot-wire elements of the a plurality of hot wire sensor elements of the flow and Vortex sensor very much robust and accurate manufacture. Furthermore the corresponding methods for mass production of such flow and vortex sensors are good suitable. An advantageous preferred use relates to the recognition from vortex for example as a noise source. This Use can be done for example in wind tunnel tests.

whirl are essential in generating noise and noise. therefore is it for the design of low noise Aircraft and aircraft parts important to identify noise and noise sources, and for this To identify vortex, which creates the structure in the flow. This can essentially only be done by measuring the vectorial properties the flow carried out become.

to Detection of turbulence is nowadays mainly laser Doppler anemometer (LDA) or a laser light-section technique (particle image velocimeter, PIV) used.

With leave the multi-hot-wire sensor according to the invention in contrast to such conventional methods also optically not accessible Measure areas. Furthermore Thus high-frequency coherent structures in the flow can be measured.

The flow according to the invention is or vortex sensor far more robust and compact executable than previously known MehrfachHitzdrahtsysteme, which are very fragile and are very time consuming and can be produced only in laborious manual production.

With the proposed invention Microfabrication technology can a plurality of Hitzdrahtsensorelementen together in one step preferably using standard MEMS technology combined with micro-assembly or μ-packaging is used. This not only allows fabrication of individual probes, but also also an array or a matrix of vector wave sensors different substrates.

So can be compared to conventional Hitzdrahtfühlermessmethoden by parallel Measurements and measuring time (eg wind tunnel time) can be saved.

in the Compared to previously used MehrfachHitzdrahtfühlern is the inventive flow or Eddy probe due to the manufacturing process a lot more robust and due of the possible Assembly and fastening process much more accurate in its construction. In addition, the same can be achieved by batch production make a variety of individual hot wire elements what the unit costs significantly reduced.

• • Es lässt sich leicht eine hohe Frequenzinformation bis hin zu einigen Kilohertz erhalten und somit ein Zeitansprechverhalten, das wesentlich besser als LDA (Grenze: 3 Kilohertz) oder PIV (Grenze: 2 Kilohertz) ist.
• • Im Gegensatz zu PIV und LDA ist keine Versetzung der Strömung mit Partikeln notwendig. Die bei den konventionellen Methoden PIV und LDA benötigte Partikelversetzung kann die Eigenschaften der Strömung beeinflussen, so dass die Messung ungenauer wird. Außerdem folgen die Partikel nicht immer genau der Strömung, insbesondere bei Drehströmungen.

Compared to PIV and LDA as alternative measuring methods for measuring the vectorial flow characteristics, the advantageous use of the flow or vortex sensor according to the invention offers the following advantages:

• • It is easy to get high frequency information up to a few kilohertz and thus a time response that is significantly better than LDA (limit: 3 kilohertz) or PIV (limit: 2 kilohertz).
• • In contrast to PIV and LDA, no displacement of the flow with particles is necessary. The particle displacement required in the conventional PIV and LDA methods can influence the properties of the flow, making the measurement less accurate. In addition, the particles do not always follow exactly the flow, especially in rotational flows.

Therefore is with the flow or the invention Eddy probe a much more accurate measurement than with previous sensors achievable.

embodiments The invention will be explained in more detail with reference to the accompanying drawings. In this shows:

1 a plan view of a first embodiment of a microfabricated Hitzdrahtsensorelements;

2 a sectional view taken along the line II-II of 1 ;

3 a plan view of a flow or vortex sensor according to a first or second embodiment, which consists of two Hitzdrahtsensorelementen according to 1 is constructed;

4 a sectional view taken along the line VV of 3 for the first embodiment of the flow or vortex sensor;

5 a section along the line VV of 3 for the second embodiment of the flow or vortex sensor;

6 an exploded view of a third embodiment of a flow or vortex sensor, which is composed of two pairs of summarized in egg ner assembly Hitzdrahttsensorelementen;

7 a plan view of an alternative embodiment of such an assembly for providing a pair of hot wire sensor elements;

8th - 11 various views of different multiheated wire sensor systems for measuring the vector of the flow velocity and / or a vortex field of a fluid, which with flow sensors according to the 3 to 7 are buildable.

In the 1 and 2 is an embodiment for a first hot wire sensor element 10 to build a flow or vortex sensor 12 shown schematically. The hot wire sensor element 10 is a building block for building a sensor system 16 , by means of which the vectorial velocity and vortex fields in complex flows can be measured.

A minimal configuration of such a sensor system 16 has the components explained in more detail below:
A base body 18 a component referred to herein as a hot wire sensor element of a flow or vortex sensor 12 is from a single substrate 20 educated. The substrate 20 is formed in a preferred embodiment of crystalline silicon. In other embodiments, gallium arsenide or quartz is used. A typical thickness D of the substrate 20 is between 100 and 700 microns.

As it turned out 1 and 2 results is a such substrate 20 so microfabricated with a standard MEMS technique that it is a baseplate 22 as a base body 18 and two elongated extensions or protrusions protruding therefrom in the form of so-called tines 24 . 25 (English: prongs) has. The tines 24 . 25 usually have a thinner thickness than the base plate 22 , The base plate 22 and the tines 24 . 25 are all made of the same material, namely the substrate material. The tines 24 . 25 are different in their length. In particular, a first tine 24 longer than a second tine 25 ,

Between end areas - in 1 between the endpoints - the tines 24 . 25 is a first wire element 26 , here in the form of an electrically conductive wire, freely suspended. The first wire element 26 forms with the first tine 24 an angle α of about 45 °. Accordingly, the first wire element forms 26 with the second prong 25 an angle of about 135 °.

The first wire element 26 serves as a heating element ("hot wire or hot wire") and is therefore hereinafter referred to as a hot wire element 26 designated. For heating, an electric current can be conducted through the hot-wire element.

The hot wire element 26 is further capable of measuring its own temperature by electrical means in the embodiments illustrated herein. This is done for the hot wire element 26 used a material with known and calibrated temperature coefficient of electrical resistance.

The the hot wire element 26 forming wire is typically made by depositing a thin film layer on the substrate 20 and then exposed by suitable (sub) etching techniques. Typical materials for the wire are polycrystalline silicon or heat-resistant and stable metals such as platinum, platinum-rhodium alloys, tungsten or gold. Other materials are possible.

The hot wire element 26 is connected to the base plate by suitable electrical connections 28 electrically connected. The electrical connections 28 show traces 30 made of a metal with low electrical resistance. The tracks 30 run electrically isolated on the structure of the tines 24 . 25 and the base plate 22 , The electrical contact with a power supply and evaluation device (not shown) via bonding pads 32 , with which contact pin 34 or other electrical contacts (eg solder joints) can be connected.

The 1 - 5 show molding a simple construction in which the hot-wire element 26 at the same time for heating and for measuring the heat convection by a fluid flow passing over it.

The 1 and 2 show a first hot wire sensor element 10 , which is in this way for measuring a first direction component of the fluid flow - substantially perpendicular to the longitudinal extent of the Hitzdrahtelements 26 - serves.

In the 3 - 7 are now several embodiments of the flow or vortex sensor 12 shown adjacent to this first hot wire sensor element 10 still a second Hitzdrahtelement 36 to measure a second directional component of the fluid flow. The second hot wire sensor element 36 is mirror image of the first Hitzdrahtelement 10 arranged and / or trained. It therefore has the same elements as the first hot wire element 10 on, with the same reference numerals are used.

In the in the 3 and 4 illustrated first embodiment of the flow or vortex sensor 12 is the first embodiment of the hot wire sensor element 10 according to 1 simply identical again as a second hot wire sensor element 36 used. For this purpose, the base plates 22 Using assembly techniques, as used in MEMS technology, accurately positioned and fixed with their backs on each other. The hot wire sensor elements 10 . 36 are thus arranged mirrored along a longitudinal central axis. As a result, form the Hitzdrahtelemente 26 of the first hot wire sensor element 10 and the second hot wire sensor element 36 an x-structure like her in 3 is apparent.

The embodiment according to 5 corresponds in the plan view of in 3 displayed view. In this embodiment of the flow or vortex sensor 12 however, use the first hot wire sensor element 10 and the second hot wire sensor element 36 the same substrate 20 , In this case, the hot wire sensor element is on one side 10 and at its rear side, the second hot wire sensor element 36 educated.

Accordingly, the flow or swirl sensor is 12 each through a single hot wire sensor element 10 . 36 according to 1 and 2 formed base structure formed at least twice in a mirror image arrangement, wherein the two Hitzdrahtsensorelemente 10 . 36 are positioned very close to each other. These in the 3 - 5 shown minimal configuration is now able to measure the fluid flow in two dimensions, since the two Hitzdrahtelemente 26 have different angular orientations.

This in 3 illustrated configuration can in a first embodiment by arranging two sensor units - Hitzdrahtsensorelement 10 . 36 as shown in 2 - be obtained by appropriate assembly techniques, as shown in 4 is shown schematically.

In a second execution, as in 5 Dagestellt are both hot wire sensor elements 10 . 36 on the same substrate 20 integrated. This embodiment leads to a very high accuracy for the alignment of the two structures and due to the integral training to a high robustness and a compact construction.

At an in 6 illustrated third embodiment of the flow or vortex sensor 12 are four hot wire sensor elements 10 . 36 , disposed near each other, each hot wire sensor element 10 . 36 . 38 . 40 is rotated by 90 ° to its adjacent Hitzdrahttsensorelement.

This is in the third embodiment of the flow or vortex sensor 12 a first assembly 42 with the first hot wire sensor element 10 and the second hot wire sensor element 36 with a second module 44 with a third hot wire sensor element 38 and a fourth hot wire sensor element 40 combined. The assemblies 42 . 44 use for their hot wire sensor elements 10 . 36 . 38 . 40 each the same substrate 20 , Here, the Hitzdrahtsensorelemente are not adjacent to each other, but arranged side by side. For connecting the modules 42 . 44 have these on a center piece corresponding notches 46 on top of each other. The two modules 42 . 44 are up to the training of their scores 46 formed identically and can be together in a common manufacturing process - for example, together on a wafer - produced.

The hot wire sensor elements 10 . 36 . 38 . 40 are at the in 6 illustrated third embodiment of the flow or vortex sensor 12 next to the first wire element - hot wire element 26 - Still with a second wire element 50 provided, which can be produced in the same way as the first wire element 26 ,

7 shows a further possible embodiment of the modules 42 . 44 (using the example of the first module 42 , the second assembly 44 is up to the arrangement of the notch 46 identical to the first module 42 ) at each hot wire sensor element 10 . 36 . 38 . 40 in addition to the second wire element 50 and the hot wire element 26 still a third wire element 52 is provided. Also the third wire element 52 is manufacturable in the same way as the hot wire element 26 ,

The second wire element 50 at 6 and the second and third wire elements 50 . 52 at 7 run parallel to the Hitzdrahtelement 26 , In the embodiment with three wire elements 26 . 50 . 52 becomes the hot-wire element 26 between the second wire element 50 and the third wire element 52 arranged.

The embodiment with only one additional wire element 50 ( 6 ) is arranged in the flow such that the second wire element 50 downstream of the hot wire element 26 is arranged. The practical arrangement of the sensors with two additional wire elements 50 . 52 ( 7 ) is preferably made such that the additional wire elements 50 . 52 upstream and downstream of the hot wire element 26 to come to rest.

These additional wire elements 50 . 52 are not heated and serve only as temperature sensors. An adequate temperature sensitivity can be achieved, for example, by a suitable temperature coefficient of its electrical resistance. For a given TCR of the sensor material, the temperature sensitivity is achieved by selecting the working temperature. High overtemperature - in relation to the ambient temperature - means high speed sensitivity, low overtemperature means low speed sensitivity. The additional wire elements 50 . 52 thus measure the heat transfer by convection from the hot wire sensor element 26 due to the fluid flow. These, formed for example by additional wires, additional wire elements 50 . 52 are also with the base plate 22 through additional electrical connections 54 connected to the surface of the tines 24 . 25 run and each other and to the substrate 20 are electrically isolated. Only electrical reference potential can be shared by the different circles.

• a) Eine mögliche Verfahrensweise ist, das Hitzdrahtelement 26 mit einem konstanten Strom zu betreiben und seine durch den strömungsinduzierten Hitzetransfer bedingte Temperaturänderung durch Erfassen einer Änderung seines Widerstandes zu messen.
• b) Eine weitere Möglichkeit ist, das Hitzdrahtelement bei einer konstanten erhöhten Temperatur zu halten wobei man die Menge der hierzu benötigten elektrischen Energie oder Leistung als Anzeige für die Geschwindigkeit der Strömung verwendet. Mit einem ordentlich entworfenen und ausgelegten Ringleitersteuerschaltkreis oder -regelschaltkreis lassen sich höhere Grenzfrequenzen erreichen als in dem Konstantstrommodus.
• c) Bei einer Mehrdrahtanordnung wie sie beispielsweise in 6 und 7 dargestellt ist, wird üblicherweise das Verfahren b) angewandt, wobei das stromaufwärtige Drahtelement 50 als ein Anzeigeelement für die Umgebungstemperatur verwendet wird. Im Falle von zwei Temperatursensordrähten kann der Temperaturunterschied zwischen den beiden Drahtelementen als direkter Anzeiger der Fluidströmung verwendet werden.
• d) Die Mehrdrahtkonstellation erlaubt zusätzlich ein sogenanntes Flugzeitkonzept für die Strömungsmessung. Die Grundidee ist, die Flugzeit zu messen, die benötigt wird, bis ein ein kurzer durch den Heizwiderstand induzierter Hitzeimpuls einen der Temperaturerfassungsdrähte erreicht. Bei den konkreten Ausführungsformen gemäß 6 und 7 würde demnach die Zeit gemessen, die vom Einleiten eines kurzen Hitzeimpulses in das Hitzdrahtelement bis zum Erfassen des Hitzeimpulses durch das zweite Drahtelement 50 oder das dritte Drahtelement 52 reicht.

With the different embodiments of the hot-wire sensor elements described above 10 . 36 . 38 . 40 can be obtained in the following ways usable temperature signals:

• a) One possible procedure is the hot-wire element 26 to operate at a constant current and measure its temperature change due to the flow-induced heat transfer by detecting a change in its resistance.
• b) Another possibility is to keep the hot-wire element at a constant elevated temperature using the amount of electrical energy or power required for this purpose as an indication of the velocity of the flow. With a neatly designed and laid out The ring conductor control circuit or regulation circuit can achieve higher cutoff frequencies than in the constant current mode.
• c) In a multi-wire arrangement such as in 6 and 7 is shown, the method b) is usually applied, wherein the upstream wire element 50 is used as an ambient temperature indicator. In the case of two temperature sensor wires, the temperature difference between the two wire elements can be used as a direct indicator of fluid flow.
• d) The multi-wire constellation additionally allows a so-called time-of-flight concept for flow measurement. The basic idea is to measure the time of flight required for a short heat pulse induced by the heating resistor to reach one of the temperature sensing wires. In the concrete embodiments according to 6 and 7 Accordingly, the time would be measured, from the introduction of a short heat pulse in the Hitzdrahtelement until detecting the heat pulse through the second wire element 50 or the third wire element 52 enough.

As in 6 indicated, the assembly of the two modules takes place 42 and 45 by being rotated 90 ° to each other and attached to each other. This gives four wire elements in each perpendicular orientation to each other. This is the minimum configuration for measuring turbulence of a turbulent flow field.

Except in the in 6 As shown, a comparable structure can also be achieved by fitting together four hot-wire sensor elements 10 according to the embodiment of 1 to be obtained.

Around all three dimensions of a vortex vector of the flow field To obtain three such 4-Hitzdrahtelemente sensors in matching arrangement combined.

Possible arrangements are in the 8th - 11 shown. These basic arrangements with the flow and vortex sensors in the Ausführungsfor men according to 1 - 7 can be realized, are explained in more detail below.

With the arrangements should at least components of the vortex vector directly be measured.

8th shows a crosswise arrangement of two hot wire elements 26 a first hot wire sensor element 10 and a second hot wire sensor element 36 in combination with two pairs of parallel further wire elements, which pairs are perpendicular to each other and perpendicular to the cross assembly.

The crosswise arrangement can by training according to 3 will be realized. Further, the parallel wires may be similar to the wire sensor elements 36 . 38 . 40 according to 3 or 7 shown also produced in microfabrication.

By such an arrangement according to 8th let the crossflow vortex components Ω _y and Ω _{z be} measured. With the two couples 60 . 62 parallel wire elements can be estimated ∂u / ∂y. With the X-arrangement, the magnitude u of the vector in the x-direction and the magnitude v of the vector in the y-direction can be estimated.

9 shows an arrangement with five hot wire elements 71 - 75 , wherein the hot-wire elements 72 and 73 similar to the assembly 42 . 44 from 6 can be formed and arranged in microfabrication technology. The remaining wire sensor elements could also be manufactured and configured using microfabrication techniques. The sensor shown can measure the flow-directed turbulence and at the same time be sensitive to the transverse vortex vector components Ω _y and Ω _z , which can be measured simultaneously.

10 shows the basic arrangement of wire elements in a 6-sensor probe 80 , which can simultaneously measure Ω _x and Ω _z or by rotation of the probe by 90 ° Ω _x , Ω _y . The six hot-wire elements 81 - 86 form four pairs of X configurations. Also these hot wire elements 81 - 86 be like with the help of 1 and 7 explained manufactured.

11 shows another five configurations with the flow or vortex sensors 12 according to 6 and / or the elements according to 1 can be achieved. In 11a three orthogonal 3-hot-wire arrays are shown. Each of these 3-wire-hot-wire arrays can be made by combining three of them 1 shown hot wire sensor elements 10 build up.

11b shows three orthogonal 4-hot-wire arrays. Each of these 4-hot-wire arrays can be controlled by a flow or vortex sensor 12 according to 6 (each in plan view from the left in 6 trained).

11c shows an arrangement of five such 4-hot-wire arrays 90 ; 11d shows an on order of three such 4-hot-wire arrays 90 and 11e shows another possible arrangement of five such 4-hot-wire arrays.

Typical magnitudes for the flow or vortex sensor 12 or the individual hot wire sensor elements 10 . 36 . 38 . 40 are, as in the 7 , indicated, a length L in the cm range (0.5 to about 5 cm), a width W _{1 of} the tines 24 . 25 in the order of 100 .mu.m of a width W _{2 of} the distance, which is bridged by the wire elements, in the range of a few 10 microns.

10

first Hitzdrahtsensorelement

12

Flow or Eddy probe

16

sensor system

18

base body

20

substratum

22

baseplate

24

first Tines (first projection)

25

second Tines (second projection)

26

first Wire element, hot wire element

28

electrical connection

30

conductor path

32

bond pads

34

contact pins

36

second Hitzdrahtsensorelement

38

third Hitzdrahtsensorelement

40

fourth Hitzdrahtsensorelement

42

first module

44

second module

46

score

50

second wire element

52

third wire element

54

electrical connection

60

first Pair of parallel wire elements

62

second Pair of parallel wire elements

71-75

Hitzdrahtelemente

80

6-sensor probe

81-86

Hitzdrahtelemente

90

4-hot wire array

L

Length of the Wire sensor element

W ₁

width the tines

W ₂

width the distance between the tines

Claims (16)

Flow or vortex sensor ( 12 ) with a first on a substrate ( 20 ) microfabricated hot wire sensor element ( 10 ) for measuring a first component of a fluid or vortex field of a fluid, and at least a second one on a substrate ( 20 ) microfabricated hot wire sensor element ( 36 ), which is at a fixed angle to the first hot-wire sensor element (FIG. 10 ) to measure at least one second component of the flow or vortex field different from the first component, characterized in that each microfabricated hot-wire sensor element ( 10 . 36 . 38 . 40 ) of a base body ( 18 ) of the substrate ( 20 ) projecting elongated projections ( 24 . 25 ) or pins, wherein between an end region of a first projection ( 24 ) or pin and an end portion of a second projection ( 25 ) or pin a hot wire element ( 26 ) freely suspended, which is adapted to pass through a through the hot wire element ( 26 ) to be heated therethrough, and that the first projection ( 24 ) or first pin in its longitudinal direction longer than the second projection ( 25 ) or second pin, so that the hot wire element ( 26 ) with respect to the base body ( 18 ) is suspended obliquely, so that by mirror image arrangement and formation of the Hitzdrahtsensorelemente ( 10 . 36 ) a different orientation of two hot wire elements ( 26 ) is reachable. Flow or vortex sensor according to claim 1, characterized in that the hot wire element ( 26 ) of the first hot wire sensor element ( 10 ) and the hot wire element ( 26 ) of the second hot wire sensor element ( 36 ) extend at an angle of about 90 ° to each other. Flow or vortex sensor according to claim 2 or 3, characterized in that the hot-wire element ( 26 ) and the first elongated projection ( 24 ) or first pin an angle (α) of about 45 ° span. Flow or vortex sensor according to one of claims 1 to 3, characterized in that the first and the second Hitzdrahtsensorelement ( 10 . 36 ) are formed and arranged mirrored around a plane or line running parallel to the longitudinal direction of the first projections or pins. Flow or vortex sensor according to one of claims 1 to 4, characterized in that the base body ( 18 ) a base plate ( 22 ) is that the projections or pins teeth or prongs ( 24 . 25 ), which extend from a narrow side of the base plate ( 22 ) from parallel to the plane of extension of the base plate ( 22 ) and that the hot-wire element ( 26 ) parallel to the plane of extension of the base plate ( 22 ). Flow or vortex sensor according to one of claims 1 to 5, characterized in that the hot-wire element ( 26 ) is configured to generate an electrical signal from which the temperature of the Hitzdrahtelements ( 26 ) is determinable. Flow or vortex sensor according to one of claims 1 to 6, characterized in that at least one of the Hitzdrahtsensorelemente ( 10 . 36 . 38 . 40 ) a second wire element ( 50 ), which is substantially parallel to the hot-wire element ( 26 ) extends with an interspaced by the flow or vortex field to be measured. Flow or vortex sensor according to claim 7, characterized in that the at least one hot wire sensor element ( 10 . 36 . 38 . 40 ) a third wire element ( 52 ) which is parallel to the hot wire element ( 26 ) and to the second wire element ( 50 ) such that the hot wire element ( 26 ) between the second ( 50 ) and third ( 52 ) Wire element is arranged and that between the Hitzdrahtelement ( 26 ) and the third wire element ( 52 ) there is an intermediate distance, which can be passed through the flow or vortex field to be measured. Flow or vortex sensor according to claim 8, characterized in that each of the hot wire sensor elements ( 10 . 36 . 38 . 40 ) an electrical connection ( 28 . 54 ) to its at least one wire element ( 26 . 50 . 52 ) whose electrical resistance is substantially lower than the electrical resistance of the wire element ( 26 . 50 . 52 ) even. Flow or vortex sensor according to one of claims 8 or 9, characterized in that the one or more wire elements ( 26 . 50 . 52 ) are formed of polycrystalline semiconductor material, in particular of polycrystalline silicon, or of a metal film, in particular of platinum, a platinum-rhodium alloy, tungsten or gold. Flow or vortex sensor according to one of the preceding claims, characterized in that the first and the second hot-wire sensor element ( 10 . 36 ) on a common substrate ( 20 ) are formed. Flow or vortex sensor according to one of the preceding claims, characterized in that the substrate ( 20 ) of the respective hot-wire sensor elements ( 10 . 36 . 38 . 40 ) is formed of monocrystalline semiconductor, in particular monocrystalline silicon. Flow or vortex sensor according to one of the preceding claims, characterized in that a third hot-wire sensor element ( 38 ) with a hot wire element ( 26 ) is provided, which is in a different direction as the Hitzdrahtelemente ( 26 ), the first and second hot wire sensor elements ( 10 . 36 ) to measure a third component of the flow or vortex field. Flow or vortex sensor according to claim 13, characterized in that a fourth hot wire sensor element ( 40 ) with a hot wire element ( 26 ) is provided, which is in a different direction as the Hitzdrahtelemente ( 26 ), the first, second and third hot wire sensor elements ( 10 . 36 . 38 ) to measure a fourth component of the flow or vortex field. Flow or vortex sensor according to claim 14, characterized in that the respective Hitzdrahtelemente ( 26 ) of the first to fourth hot wire sensor elements ( 10 . 36 . 38 . 40 ) each extend at a substantially right angle to each other. Flow or vortex sensor according to one of the preceding claims, characterized in that a plurality of at least each of a first and a second Hitzdrahtsensorelement ( 10 . 36 . 38 . 40 ) formed hot-wire sensor units ( 42 . 44 ) are arranged at different angles to each other spatially in the vicinity of each other.