GB2294767A - Hot-wire flow rate measurement - Google Patents
Hot-wire flow rate measurement Download PDFInfo
- Publication number
- GB2294767A GB2294767A GB9420066A GB9420066A GB2294767A GB 2294767 A GB2294767 A GB 2294767A GB 9420066 A GB9420066 A GB 9420066A GB 9420066 A GB9420066 A GB 9420066A GB 2294767 A GB2294767 A GB 2294767A
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- GB
- United Kingdom
- Prior art keywords
- hot
- wire
- fluid
- wire element
- flow
- 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.)
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Classifications
-
- 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
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
-
- 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
-
- 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
- G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
- G01F1/6986—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters with pulsed heating, e.g. dynamic methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
- G01P5/12—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables using variation of resistance of a heated conductor
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Measuring Volume Flow (AREA)
Abstract
Hot-wire flow rate apparatus for measuring a flow characteristic of a fluid, for example the velocity of moving air or other gas or gases, comprises a transducer including at least one hot-wire element which in use is positioned in a flow path of the fluid under measurement, supply means for supplying electrical current pulses to the hot-wire element to heat the latter, and sensing means for sensing the resistance of the hot-wire element when heated by the supply means for use in measuring the flow characteristic of the fluid. As described the pulses are of constant amplitude and have a duration of a few milliseconds, determined by a computer clock source. The time tstp taken for the element to reach a set value of resistance Rstp (corresponding to a set temperature) is a function of the fluid velocity U. An arrangement using a number of hot-wire elements on the surface of a body to map the the fluid flow over the body is described. <IMAGE>
Description
Hot-wire Flow Rate Measurement
This invention relates to a hot-wire flow rate apparatus and system for measuring flow characteristics of a fluid, for example the velocity of moving air or other gas or gases. The invention also relates to a method of measuring fluid flow characteristics, e.g. rates of fluid flow. In particular, but not exclusively, the invention finds application in mapping fluid flow over a body positioned in a fluid flow path.
Conventional apparatus for fluid flow rate measurement comprise hot-wire anemometers which are either operated in constant current mode or constant temperature mode. Such hot-wire anemometers operate on the principle that the resistance of the hot-wire element changes markedly with temperature. In constant current mode a steady electrical current is applied continuously to the hot-wire element which is positioned in the fluid flow path. Since the temperature that the hot-wire element attains is dependent on the velocity of the fluid flow, the resistance of the hot-wire element provides an indication of the fluid flow velocity.In constant temperature mode, the hot wire element is placed in the fluid path and the amount of heating current which has to be continuously applied to maintain the temperature, or resistance, of the hot-wire element at a constant value provides an indication of the velocity of the fluid flow.
The present invention seeks to provide hot-wire flow rate measuring apparatus in which power is supplied to at least one hot-wire element in pulsed form.
According to one aspect of the present hot-wire flow rate measuring apparatus comprising transducer means which includes at least one hot-wire element and which in use is intended to be positioned in a flow path of a fluid under measurement, supply means for supplying electrical power to said hot-wire element(s) for heating the latter, and sensing means for sensing the resistance of the hot-wire element(s) when heated by said supply means for use in measuring flow characteristics of the fluid being measured, is characterised in that said supply means is arranged to supply current pulses to the hot-wire element(s) for heating the latter.
Typically the current pulses have a duration of only a few milliseconds (ms), and thus relatively high current values can be used without risk of burn out. Also the large signal magnitudes provided by the current levels used, together with the on/off nature of the control, combine to simplify the design of the system electronics.
Preferably the apparatus comprises timing means for determining the length of time taken for the hot-wire element(s) to be heated to an elevated predetermined temperature, sensed by said sensing means, when positioned in the fluid flow path and supplied with said current pulses, said length of time providing an indication of the velocity of fluid flow being measured. This preferred embodiment of the invention delivers fluid flow velocity information in the form of a time interval rather than a voltage or current as provided with conventional anemometer systems. This time interval is small, typically in the order of milliseconds (ms) or less (fractions of ms).In a particularly preferred embodiment of the invention the transducer means comprises a plurality, e.g. 32 or 64, hotwire elements in an array and the sensing means is arranged to scan the individual hot-wire elements sequentially under computer control. The hot-wire elements are suitably positioned over the surface of a body to be analysed to enable the creation of a "map" of fluid flow over the body when the body is positioned in a fluid flow path. As the "n" hot-wire elements are multiplexed to a single acquisition system there is a substantial saving in hardware over "n" conventional systems. Furthermore, because the time interval is short compared to the "steady state time", the apparatus offers speed advantages over conventional constant current systems.
According to another aspect of the present invention a method of measuring a flow characteristic, e.g. flow rate, of fluid in a flow path comprising positioning a transducer, including at least one hot-wire element, in the flow path, supplying current to the transducer to heat the hot-wire element(s) and sensing the resistance of the heated hot-wire element(s) for use in measuring the flow characteristic of the fluid in said flow path, is characterised in that said current is supplied to the transducer in pulse form.
Preferably the length of time is measured for the hot-wire element(s) to be heated to an elevated predetermined temperature, which time interval provides an indication of the velocity of fluid flow in said flow path.
The heating current is conveniently supplied in discrete pulses of constant magnitude and, since the current pulse is discontinued after a typical heating period of only a few ms, relatively high current can be used without risk of burn out. It is also possible to heat the hot-wire element(s) by pulsed current having a pulse repetition rate which is short compared with the cooling time constant. If a plurality of hot-wire elements are arranged in an array over the surface of a body, a "map" of the fluid flow over the body can be created.
According to a still further aspect of the present invention there is provided a hot-wire measuring system for providing a map of a fluid flow characteristic of a gas or gases flowing over the surface of a body, comprising a plurality of hot-wire elements arranged over the surface of the body to be mapped, means for supplying pulsed heating current to the hot-wire elements and timing means for timing the length of time each hot-wire element takes to be heated to an elevated predetermined temperature to enable the creation of said map.
Embodiments of the invention will now be described, by way of example only, with particular reference to the accompanying drawings, in which:
Figure 1 is a graph showing the free stream velocity
relationship for a flat plate element in a fluid flow;
Figure 2 is a graph showing a boundary layer profile for
a flat plate element in a fluid flow;
Figure 3 is a block diagram of a system for providing
fluid flow distribution information for a fluid flowing
over a cylinder;
Figure 4 is a schematic perspective view of a cylinder
element carrying a plurality of hot-wire transducer
elements forming part of the cylinder of the system shown
in Figure 3;
Figure 5 is a side view of the cylinder element shown in
Figure 4 incorporated into a cylinder;
Figure 6 is a calibration curve showing the relationship
between shear stress values and set temperature point
acquisition times; ;
Figure 7 is a graph of set temperature point acquisition
times for a single hot-wire transducer element carried on
a cylinder at different angular positions of the
cylinder;
Figure 8 is a graph of set temperature point acquisition
times for a plurality of hot-wire transducer elements
carried on a cylinder for two different fluid flow rates
and for two sdifferent angular positions of the cylinder
offset 90 degrees from each other;
Figure 9 shows the shear stress distribution around the
cylinder computed from set temperature point acquisition
times;
Figure 10 is a graph showing the theoretical resistance
variation with time, as a result of heting and cooling,
of a hot-wire transducer element subjected to heating
current pulses;
Figure 11 shows one of the heating/cooling cycles of
Figure 10 on an expanded time scale; and
Figure 12 is a block diagram of another system for
providing fluid flow distribution information for a fluid
flowing over a cylinder.
The present invention is based on the following theoretical analysis of a platinum (Pt) hot-wire element carried between end supports, positioned in a wind field and subjected to a constant heating current. In this analysis, the various terms used are defined as follows: Ai = cylinder element correction constant
As = surface area of the wire element
Bi = cylinder element correction constant
Co = temperature coefficient of platinum
resistivity
c = thermal capacity constant of the wire cp = specific heat of the fluid at constant
pressure
Cw = specific heat of the wire
d = wire diameter I = heating current
k = thermal conductivity of the fluid
1 = length of the wire element
Nu = Nusselt number
Re = Reynold number
R = resistance ratio
RT = set temperature point (STP) resistance ratio R55 = steady state heating resistance R5tp = set temperature point (STP) resistance Rw = wire resistance at a given elevated
temperature
Rwo = wire resistance at reference temperature TW1 = active wire time constant
Tw2 = passive wire time constant
t = time tl = end of heating time
t2 = end of cooling time tstp = set temperature point (STP) acquisition time
U = free stream velocity of the fluid UL = lower limit of free stream velocity
u = local surface velocity = = absolute viscosity of the fluid
v = volume of the wire element ee = electrical resistivity of the wire element
= = mass density of the wire The active and passive time constants of the wire are given by:
Twi and TW2 represent the time constants of the heating up and cooling down processes respectively. Both are functions of U through Nu.
An important property of platinum which is fundamental to hot wire anemometry is its temperature coefficient of resistivity, where Rw =Rwo [ 1 + Co (0w - 0wo)l (3)
When a constant current I is applied to a wire, a heating effect I2RW is generated, where Rw is a function of time. Some of this heat accumulates in the wire and causes the temperature to rise, some of it is lost by convection and some by conduction at the wire ends.A heat balance equation is:
Heat Generated = Heat Accumulated + Heat Convected
+ Heat Conducted
When l/d > 1000, the heat conduction to both end supports can be neglected and a heat balance equation may be written:
Assuming that U and I are constant, the solution for
Rw from (4) is given by:
Consideration of Twi, which cannot be zero or negative, indicates a lower velocity limit, UL, for the method.Using Kramers's law, an approximate equation is derived and
Equation (5) can be written in terms of t:
If a set temperature point (or "STP") is chosen, the
STP acquisition time is given by:
From (8) it can be seen that for a system in which l/d, I and Rstp are fixed, and l/d is large enough for end conduction to be negligible, tstp is purely determined by the velocity measurand, U through the wire heating time constant Twi That is, if the time taken to reach a given temperature point is known, the velocity of the flow can be obtained.
The above analysis is based on the conditions that U > UD, the lower velocity limit, and TW2 < t2, the wire cooling time.
On the basis of this theoretical analysis, two prototype measurement systems have been developed to test the theory. In the first system, a flat perspex plate was made with streamlined ends. A single platinum (Pt) hot-wire element having l/d = 1000 was positioned 180 mm away from the leading edge of the plate and 15 mm above its surface.
The STP was set to 1550C and in a series of measurements the relationship between stp and the free stream velocity U was obtained as shown in Figure 1 (all data being averaged from 200 samples). The height of the single hot-wire element above the plate surface was adjustable against a scale and, in a second series of measurements, the variation of tstp with plate/element separation was measured. With the aid of the results shown in Figure 1, a boundary layer profile for the plate was constructed as shown in Figure 2, where 6 is the thickness of the boundary layer (about 12mm for the conditions).
In the second system illustrated schematically in block diagram from in Figure 3, the quantification of local shear stress distribution over the surface of a cylinder was chosen as an illustrative example of the application of the method to the multi-element quantification of distributed flow variations. A transducer array 1 was formed by arranging 32 equally spaced platinum hot-wire elements 2 (see Figures 4 and 5) on the outside of a cylinder 3 of "Tufnol" (trade mark), the ends of the elements 2 being turned radially inwards and being carried on internal posts (now shown). The overall length of each element was 32 mm, with 22 mm exposed on the outside of the cylinder 3, and l Zd = 1600.The transducer body formed by the cylinder 3 and hot-wire elements 2 was fitted to cylindrical aluminium sections 5a, Sb to form a composite cylinder 6 of overall length 450 mm. The location of the hot-wire elements 2 in relation to the surface is important for the measurement of boundary conditions and they were arranged so as to only touch the surface of the cylinder 3 rather than being incorporated within the surface of the cylinder.
The experimental data acquisition system shown in
Figure 3 comprises a computer interface, a transducer management system and the transducer array on the cylinder 6. Suitably interfacing of a computer 10 is via a PC14AT
I/O interface card. The heating current setting I is specified by software; a digital "word" representing its desired value being relayed via the I/O interface to a current generator 11 which has the function of translating the "word" into a continuous output current. The current is delivered to a target element 2 by a current switch 12 under the direction of an address, also specified by software and relayed via the interface.
The acquisition process uses a computer resident 129.8 kHz clock source as a timing standard. This source is divided by 2048 to provide a 63.4 Hz clock rate for the current switch, giving a current pulse width (and therefore a maximum value for tstp) of 7.89 ms. If for any reason a particular period of time occurs when there is no requirement for the heating of any element, the current may be directed to a dummy load. Thus the transient delays associated with switching the current off and on are avoided.
The signal in the form of the differential voltage IRWo produced across the wire is amplified and converted to a single-ended quantity by a differential amplifier 13. A comparator 14 compares the signal voltage with the voltage analogue of the set temperature point, STP. When these values coincide, the comparator 14 changes state, and this change is communicated to the interface. The interval between the current switch time and the comparator change of state defines tstpi which is measured by clocking a counter in the interface with the 129.8kHz clock source over its duration. The time measurement resolution is thus 7.7 ys, there being 1024 timing pulses in the maximum stp duration of 7.89 ms.
In a typical multi-element application, individual elements are scanned by the direction of heating pulses to each in turn, with t values for a universal STP being recorded.
From the theoretical analysis above, the STP acquisition time, tstpi is shown to be a function of the cross flow velocity, therefore in a multi-element application, the range of t values so recorded conveys the velocity variation over the region of their deployment.
The calibration of the hot-wire elements 2 was performed using the same equipment as was used for the single element test described above. In particular, a single element 2 was identified as a standard and a calibration element was manufactured to be an exact match in the terms of its resistance and heating characteristics.
The calibration element was located 100 mm away from the leading edge, and on the surface of, the flat plate (y = 0.02mm). With an STP setting of 1600C (R = 1.55 ohms), a series of tstp were recorded for different free stream velocities U. The shear stresses on the surface of the plate were thus obtained for each U. It has been demonstrated that, given the condition 0 < y/S < 0.03, shear stress decreases as y/5 decreases, and this condition applies to the case in question, where y = 0.02mm, y/5 = 0.005 and t5 = 0.65 nO Thus for the range of shear stress values corresponding to the different free stream velocities, U, the relation between t5 and tstp was found and is shown in Figure 6.
Since there existed initial differences between cylinder elements, the behaviour of each was not identical with the standard. Measurements demonstrated that they all presented the same flow profile but with a differing amplitude. The sensitivity of each element can be normalised to the standard by the application of the linear relation: tstpli = Ai + Bi tstpij where i, 1 to 32, is the number of the hot-wire element; j, 1 to 32, is the position of the hot-wire element relative to the stagnation point"; and tstpij is the output of the calibrated element. Ai and Bi were calculated over the U range of interest, so allowing the normalisation of each element's response in multi-element measurements.
After calibration, the cylinder 6 was mounted horizontally in the middle of the working section of a wind tunnel and, at an STP setting of 1600C, tstp data were recorded from each element for each step of a 32 step sequence describing a 3600 scan of the cylinder 6. This sequence was repeated for a second free stream speed. The results for the calibrated single element are shown in
Figure 7 and Figure 8 shows the normalised results obtained simultaneously from each element for both free-stream speeds, together with comparative results for a 900 cylinder rotation. The shear stress distribution around the cylinder can be computed from the tstp values obtained from the element array and Figure 9 shows the results obtained from the standard cylinder element compared with known results obtained for a Stanton tube.
In the prototype systems, the theoretical lower velocity limit for the value of current used (0.28A) was 4.2 m/s. For the conditions of forced convection arising from the free stream velocities above this limit, there was good agreement between theoretical and practical results.
For low velocity fluid flow (say U < lm/s) and short heating time duration, the value of tstp in equation (8) is not valid. Heat accumulates in the wire since the cooling time period is reduced. The theoretical analysis can be further developed as described below.
When the heating time of the wire is very short (with respect to To1 ), the resistance variation with time within the heating pulse may be considered to be linear, i.e., when the wire is heated from an initial state, the resistance at the end of a heating pulse of time tl, is:
Substituting for Rw from (5) into (9):
and the resistance at the end of the cooling time, time t2, is:
At balance, when the heat generated on heating is equal to the heat lost on cooling,
where R'Wo is the initial resistance at balanced state, and,
Substituting for RWtl from (12) into (13):
Then, for the heating process afterwards,
and the STP acquisition time tStp is given by::
Equation (16) shows that for the application of the method in which tl, t2, STP and I are fixed, tgtp is still a function of U through the wire cooling time constant TW2.
Figure 10 illustrates the cylical nature of wire resistance variation during the heating/cooling process. If one of the cycles is time-expanded, as shown in Figure 11, a clearer view is obtained of the conversion of sensed velocities to time data. It can be seen that tstp depends on the temperature elevation of the wire at the start of the heating process which in turn conveys the sensed velocity.
Figure 12 shows a schematic block diagram for another prototype system based on the further theoretical analysis.
The system shown is similar in many respects to the system shown in Figure 3 and it will be realised that the system shown in Figure 3 could be used instead. In the Figure 12 embodiment the acquisition method uses a computer resident 4154304 HZ clock source as a timing standard. This source is divided by software to provide various clock rates for the current switch, giving current pulse width (and therefore a maximum value for step) and counting clock rate.
If for any reason there occurs a particular period of time when there is no requirement for the heating of any element, the current may be directed to a dummy load. Thus the transient delays associated with switching the current off and on are avoided.
The signal in the form of the differential voltage IRw produced across the wire is amplified and converted to a single-ended quantity by a differential amplifier. A comparator compares the signal voltage with the voltage analogue of the set temperature point, STP. When these values coincide the comparator changes state, and this change is communicated to the interface. The interval between the current switch time and the comparator change of state defines tStp, which is measured by clocking a counter in the interface with the clock source over its duration.
In this application, the heating pulse width is set to 7.89 ms and the counting clock rate is 130 kHz; thus the time measurement resolution is 7.7 zs, there being 1024 timing pulses in the maximum tstp duration of 7.89 ms.
The invention describes a pulsed method of heating one or more hot-wire elements. In particular, but not exclusively, the length of time taken for a hot-wire element to be heated to an elevated predetermined temperature is used to calculate fluid flow parameters.
Claims (12)
1. Hot-wire flow rate measuring apparatus comprising transducer means which includes at least one hotwire element and which in use is intended to be positioned in a flow path of a fluid under measurement, supply means for supplying electrical power to said hot-wire element(s) for heating the latter, and sensing means for sensing the resistance of the hot-wire element(s) when heated by said supply means for use in measuring flow characteristics of the fluid being measured, characterised in that said supply means is arranged to supply current pulses to the hot-wire element(s) for heating the latter.
2. Apparatus according to claim 1, in which said supply means is adapted and arranged to supply said current pulses with a duration of only a few milliseconds (ms).
3. Apparatus according to claim 1 or 2, further comprising timing means for determining the length of time taken for the hot-wire element(s) to be heated to an elevated predetermined temperature, sensed by said sensing means, when positioned in the fluid flow path and supplied with said current pulses, said length of time providing an indication of the velocity of fluid flow being measured.
4. Apparatus according to any of the preceding claims, in which the transducer means comprises a plurality, of hot-wire elements in an array and the sensing means is arranged to scan the individual hot-wire elements sequentially under computer control.
5. A method of measuring a flow characteristic, e.g. flow rate, of fluid in a flow path comprising positioning a transducer, including at least one hot-wire element, in the flow path, supplying current to the transducer to heat the hot-wire element(s) and sensing the resistance of the heated hot-wire element(s) for use in measuring the flow characteristic of the fluid in said flow path, characterised in that said current is supplied to the transducer in pulse form.
6. A method according to claim 5, in which the length of time is measured for the hot-wire element(s) to be heated to an elevated predetermined temperature, which time interval provides an indication of the velocity of fluid flow in said flow path.
7. A method according to claim 5 or 6, in which the heating current is supplied in discrete pulses of constant magnitude.
8. A method according to claim 5 or 6, in which the or each hot-wire element is heated by pulsed current having a pulse repetition rate which is short compared with the cooling time constant.
9. A method according to any of claims 5 to 8, in which a plurality of said hot-wire elements are arranged in an array over the surface of a body and a "map" the fluid flow over the body is created.
10. A hot-wire measuring system for providing a map of a fluid flow characteristic of a gas or gases flowing over the surface of a body, comprising a plurality of hotwire elements arranged over the surface of the body to be mapped, means for supplying pulsed heating current to the hot-wire elements and timing means for timing the length of time each hot-wire element takes to be heated to an elevated predetermined temperature to enable the creation of said map.
11. Hot-wire flow rate measuring apparatus constructed and arranged substantially as herein described with reference to the accompanying drawings.
12. A method of measuring a flow characteristic of a fluid in a flow path, the method being substantially as herein described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9420066A GB2294767A (en) | 1994-10-05 | 1994-10-05 | Hot-wire flow rate measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9420066A GB2294767A (en) | 1994-10-05 | 1994-10-05 | Hot-wire flow rate measurement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9420066D0 GB9420066D0 (en) | 1994-11-16 |
| GB2294767A true GB2294767A (en) | 1996-05-08 |
Family
ID=10762371
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9420066A Withdrawn GB2294767A (en) | 1994-10-05 | 1994-10-05 | Hot-wire flow rate measurement |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2294767A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003034002A1 (en) * | 2001-10-10 | 2003-04-24 | E+E Elektronik Ges.M.B.H. | Airspeed sensor and method for operating an airspeed sensor |
| EP2368127A1 (en) * | 2008-12-19 | 2011-09-28 | Commissariat à l'Énergie Atomique et aux Énergies Alternatives | Anemometer probe having one or more wires and its method of production |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4334186A (en) * | 1979-10-03 | 1982-06-08 | Hitachi, Ltd. | Apparatus for driving hot-wire type flow sensor |
| WO1985000059A1 (en) * | 1983-06-17 | 1985-01-03 | Institut De Recherche Et De Developpement Aërologi | Measuring apparatus for the determination of wind speed |
| US4501145A (en) * | 1981-07-13 | 1985-02-26 | Battelle Memorial Institute | Immersion thermal exchange parameter determination |
| EP0164729A2 (en) * | 1984-06-13 | 1985-12-18 | Nippondenso Co., Ltd. | Control system for an engine |
| US4693115A (en) * | 1984-04-24 | 1987-09-15 | Nippon Soken, Inc. | Device for measuring flow rate of air |
| GB2209402A (en) * | 1987-09-02 | 1989-05-10 | Hitachi Ltd | Measuring air intake of ic engine |
-
1994
- 1994-10-05 GB GB9420066A patent/GB2294767A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4334186A (en) * | 1979-10-03 | 1982-06-08 | Hitachi, Ltd. | Apparatus for driving hot-wire type flow sensor |
| US4501145A (en) * | 1981-07-13 | 1985-02-26 | Battelle Memorial Institute | Immersion thermal exchange parameter determination |
| WO1985000059A1 (en) * | 1983-06-17 | 1985-01-03 | Institut De Recherche Et De Developpement Aërologi | Measuring apparatus for the determination of wind speed |
| US4693115A (en) * | 1984-04-24 | 1987-09-15 | Nippon Soken, Inc. | Device for measuring flow rate of air |
| EP0164729A2 (en) * | 1984-06-13 | 1985-12-18 | Nippondenso Co., Ltd. | Control system for an engine |
| GB2209402A (en) * | 1987-09-02 | 1989-05-10 | Hitachi Ltd | Measuring air intake of ic engine |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003034002A1 (en) * | 2001-10-10 | 2003-04-24 | E+E Elektronik Ges.M.B.H. | Airspeed sensor and method for operating an airspeed sensor |
| EP2368127A1 (en) * | 2008-12-19 | 2011-09-28 | Commissariat à l'Énergie Atomique et aux Énergies Alternatives | Anemometer probe having one or more wires and its method of production |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9420066D0 (en) | 1994-11-16 |
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