GB2449654A - Airflow sensor - Google Patents

Airflow sensor Download PDF

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Publication number
GB2449654A
GB2449654A GB0710236A GB0710236A GB2449654A GB 2449654 A GB2449654 A GB 2449654A GB 0710236 A GB0710236 A GB 0710236A GB 0710236 A GB0710236 A GB 0710236A GB 2449654 A GB2449654 A GB 2449654A
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GB
United Kingdom
Prior art keywords
sensor according
air sensor
air
feedback circuit
semiconductor devices
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Granted
Application number
GB0710236A
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GB2449654B (en
GB0710236D0 (en
Inventor
Rod Hine
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.)
HAVGUARDIAN Ltd
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HAVGUARDIAN Ltd
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Publication date
Application filed by HAVGUARDIAN Ltd filed Critical HAVGUARDIAN Ltd
Priority to GB0710236A priority Critical patent/GB2449654B/en
Publication of GB0710236D0 publication Critical patent/GB0710236D0/en
Publication of GB2449654A publication Critical patent/GB2449654A/en
Application granted granted Critical
Publication of GB2449654B publication Critical patent/GB2449654B/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B25HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25FCOMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • B25F5/008Cooling means
    • 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 a meter in a continuous flow
    • G01F1/68Measuring 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
    • G01F1/684Structural 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 a meter in a continuous flow
    • G01F1/68Measuring 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
    • G01F1/684Structural 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
    • G01F1/6888Thermoelectric elements, e.g. thermocouples, thermopiles
    • 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 a meter in a continuous flow
    • G01F1/68Measuring 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
    • G01F1/696Circuits therefor, e.g. constant-current flow meters
    • G01F1/698Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01PMEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00Indicating or recording presence, absence, or direction, of movement
    • G01P13/0006Indicating or recording presence, absence, or direction, of movement of fluids or of granulous or powder-like substances
    • G01P13/006Indicating or recording presence, absence, or direction, of movement of fluids or of granulous or powder-like substances by using thermal variables
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01PMEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/10Measuring 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
    • G01P5/12Measuring 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

Abstract

An air sensor comprises a blade on which a pair of semiconductor devices 2, 4 are surface-mounted and electrically connected in series. The blade is disposed in sealed manner, in an airflow path between a source of pressurised air and a pneumatically driven machine tool, and the sensor further comprises a feedback circuit, inputs of which are provided by the voltages across the devices 2,4. The feedback circuit ensures that the difference between the voltages across each semiconductor device, being indicative of the difference in the temperatures thereof, is maintained constant by varying the current through the devices as air flow past the devices 2,4 changes. The feedback circuit further includes or is connected to a comparison means, and visual indication means being one or more LEDs (12, 14 see fig 1c). A comparison is made between actual operating current flowing through the semiconductor devices 2,4 and a programmed or stored value indicative of quiescence. Depending on the comparison result, the comparison means causes illumination or extinction of one or more of the LEDs (12, 14).

Description

Airflow Sensor This invention relates to an airflow sensor, and more
particularly to an airflow sensor, and further specifically to a means of configuring such for use in determining whether pneumatically driven machines are operating.
BACKGROUND
Operatives of industrial machinery are becoming subject to health and safety restrictions, in particular restrictions on the length of time operatives are considered to be capable of safely operating different types of pneumatically driven, hand-held machine tools Furthermore, not only are safe limits being imposed on operatives from the point of view of fatigue in operating such machinery, one of the major industrial maladies affecting operatives of such machinery is Hand Arm Vibration Syndrome (HAVS) or Vibration White Finger, which affects the circulatory and muscular systems.
The primary cause of such ailments is the transfer of vibration from powered handheld tools.
In effort to provide a simple and effective means of determining the length of time operatives have been working, and with which type of tools, GB2418252 discloses a time measurement device which measures the cumulative amount of time a tool has been in use, and is also provided with a facility for transmitting data relating to the measured time to a data collection device (e.g. PDA). The transmission may be wireless (e.g. radio frequency or infrared). In a particular embodiment, a measurement device may be incorporated into the electric plug of the tool and may comprise a sensor which detects the flow of current to the tool. A visual display may further be incorporated into the electric plug, which is thus a proprietary item, to show the elapsed time during which the tool has been in operation. Alternatively the sensor may be an accelerometer which determines when the tool is operating by sensing vibrations. The vibration exposure of the operator of the tool may be displayed. Alternatively, in the case of a compressed air tool, the sensor may detect the flow of air through the tool, and such may be achieved by means of an impeller rotationally mounted on a spindle inside the pneumatic connector by means of which the tool is connected to a supply of pressurised air, as schemitcally illustrated in Figure 5 of this document. A sensor provided in conjunction with the impeller is thus capable of determining both whether the tool is being operated, and in particularly sensitive configurations, to what extent. It is thus possible to make accurate calculations of the extent to which an operative may be fatigued as a result of the use of that particular tool and others in cumulative manner, and to prevent further use of that tool or others if a particular operative is considered to have been operating tools (which may be rated according to their propensity to cause HAVS) for a pre-determined time period, whether constantly or intermittently, in any particular day. It is also possible for a system such as described to provide operational time data on all the various operatives logged on the monitoring system, thus allowing tool hire companies to make appropriate charges and for employers to determine whether operatives are performing adequately.
The above document also describes a different type of air sensor which involves the use of a piston and cylinder arrangement wherein the piston moves within the cylinder during air flow, said sensor measuring the extent to which the piston moves to provide both an indication that the tool is operating, and optionally to what extent.
In terms of other relevant technology, a well known physical phenomenon for determining whether air is flowing through a particular conduit or past a particular location therein is hot wire anemometry. The basic principle is to provide a sufficient current through a resistive wire disposed within a conduit where air is intended to flow to cause the wire to become hot and radiate heat stably. As air flow within the conduit increases, the temperature of the wire falls, and depending on the correlation between the resistivity of the wire and its temperature, its resistance varies, most often in linear proportion with the temperature. Accordingly, as the temperature of the wire falls, the resistance also falls, and the current increases depending on the relationship between the current and the temperature of the wire in ambient conditions. Accordingly, the principle in hot wire anemometry is to provide a circuit whereby the temperature of the wire is maintained at a constant temperature as the air flow around the hot wire changes, and to determine, from the reduction (or increase) in current required to maintain the temperature of the wire, the extent to which air is flowing.
Conventional hot wire anemometry, and in particular where a thermistor is employed (essentially a temperature-sensitive resistive component, including a simple tungsten wire) is dependent to a certain degree on the temperature of the air flowing around the device, and through the year within industrial premises, the temperature of pressurised air delivered to pneumatic machine tools can vary considerably, possibly by as much as up to 10-20 C. In the context of providing a reliable indication of the extent to which air is flowing past the device, this has very important consequences, and in particular gives rise to false indications of air flow, and thus tool operation or inactivity. Therefore, a simple hot wire anemometer cannot usefully be employed within standard machine tool pneumatic connectors.
A variety of difficulties exist with currently available mechanically operating flow-detection devices. For instance, a simple flow switch based on displacement of a plunger or flap by air-flow are unsuitable for this application because of the obstruction to air-flow.
Mechanical flow-meters based on rotating varies, impellers or turbines are prohibitively expensive. Also, use of rotating parts incurs an unnecessary maintenance liability. Flow-meters based on Coriolis force, lasers, ultrasonics are similarly too expensive.
It is thus an object of this invention to provide an airflow sensor that is low-cost and capable of being mounted in standard pneumatic airline fittings, offering negligible obstruction to the airflow and capable of giving on/off indication of "trigger time" for a range of air-tools.
It is a further object of this invention to provide an air sensor which is generally insensitive to changes of temperature of the air in the pneumatic delivery system, at least over a range suitable for particular climatic regions of the world.
It is a yet further object of the invention to provide an air sensor whose operating parameters and characteristics are capable of being adjusted in-situ to suit the pressure in the system and the on/off threshold flows (i.e. a particular flow rate above which the device is considered to be operating) applicable to wide variety of pneumatically driven tools. It is also an object of this invention to provide a means of quickly and reliably configuring such a device for different tools, air pressures, air flow rates, and the like.
It is still further aspect of this present invention to embody the principles of hot wire anemometry in a device for determining air flow within a pneumatic connector, and to provide a connector incorporating such a sensor.
BRIEF SUMMARY OF THE DISCLOSURE
According to the present invention there is provided an air sensor comprising a blade on which a pair of semiconductor devices are surface-mounted and electrically connected in series, said blade being disposed in the airflow path between a source of pressurised air and a pneumatically driven machine tool, and wherein said sensor further comprises a feedback circuit, inputs of which are provided by the voltages across said semiconductor devices, the difference between which is indicative of the difference in the temperatures thereof, there being applied a potential difference across said semiconductor devices and a current thus flowing therethrough, and said feedback circuit being capable of varying one of these parameters, the other being retained substantially constant so as to effectively retain the temperature difference between said semiconductor devices substantially constant, said feedback circuit further including a comparison means, together with visual indication means, which makes a comparison between the actual operating voltage applied to, or current flowing through, said semiconductor devices and a predetermined value indicative of an absence of airflow, and depending on the result of said comparison, said comparison means causes illumination or extinction of said visual indication means.
Preferably, the blade is a separately detachable component from the feedback circuit which ideally mounted on a separate printed circuit board to allow for easy replacement of the blade in the event of degradation of the surface mounted semiconductor devices due to foreign bodies in the airflow, or corrosion thereof due to water vapour.
Preferably, the semiconductor devices, and preferably the entire blade, is coated with a conformal silicone or other protective coating.
Most preferably the semiconductor devices are transistors.
Preferably one of the transistors is diode connected and acts as a "cold" reference temperature sensor, the alternate transistor operating conventionally, and electrically connected in series with said one transistor, inputs to said feedback circuit being derived from the base-emitter Voltages (V) of each of said transistors such that the differential iVbe is indicative of the temperature difference between the alternate (hotter) transistor and reference transistor.
Most preferably the transistors are silicon NPN transistors.
In a preferred arrangement, the feedback circuit includes a user programmable component, such as a microcontroller unit, most preferably a PlC microcontroller electrically connected to one or more LEDs, said component being programmed to illuminate said one or more LEDs when certain of the conditions programmed is satisfied or not satisfied, and further being connected to a voltage or current varying device which allows for adjustment of at least one output of said microcontroller.
Most preferably, said microcontroller is connected to and drives said one or more LEDs in a manner which allows a user, through non-illumination, intermittent illumination and/or continuous illumination, of said LEDs, to set the optimum working current for the feedback circuit, the illumination of said LEDs occurring as the user changes the setting of the voltage or current varying device connected to said microcontroller.
Preferably, the microcontroller is connected to and drives two LEDs of different colours, the respective illumination in intermittent or continuous manner of which is indicative firstly that the optimum working current is less than a predetermined percentage (preferably 90% or less) of an experimentally determined quiescent, stable current value Cq for the sensor, and secondly that the optimum working current is in an acceptable range (preferably between 90% and 110%) of Cq, and thirdly that the optimum working current is greater than a predetermined percentage of Cq (preferably 110%).
Most preferably, the voltage or current varying device is a precision multi-turn potentiometer.
In normal circumstances, pressurised air is delivered at around 8bar, but modification of the electronic components in the feedback circuit may be required in the event that the system air pressure is changed substantially.
In a further preferred arrangement, the microcontroller is connected to and drives three LEDs, being green, yellow and red, illumination of the third LED being indicative of airflow to the machine tool, and thus operation thereof.
Most preferably, the blade is mounted in a multi-way (preferably four-way) manifold block which is connected in series between the pressurised air supply and the hose which feeds the machine tool thus occupying two ports thereof, the blade occupying a third port thereof and being mounted within said block most preferably in an end-on manner such that the air flows over the broader surfaces thereof on which said semiconductor components are surface mounted.
In a most preferred arrangement, a fourth port of the manifold block is provided with a non-return valve and a common bleed valve. This ensures that when one of the four channels of the manifold block is active, the three quiescent channels remain pressurised. Without this feature, restoring full air flow to unpressurised channels causes momentary air-flows which can then falsely trigger the sensor.
A specific embodiment of the invention will now be provided by way of example with reference to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures lA-i F provide a circuit diagrams of the various electronic components employed in the invention.
DETAILED DESCRIPTION
Referring firstly to Figure 1A, there is shown a pair of series connected NPN transistors 2, 4, the latter (4) being wired as a diode and acting as a reference sensor. Such components are mounted on a simple blade of PCB material, and connected as shown by the dotted lines to a feedback circuit indicated generally at 6.
Tiny surface-mount silicon transistors were chosen because: -they are very cheap (less than GBPO.03 each), -have very small thermal mass so respond very quickly, and -have a fairly consistent temperature coefficient at the base-emitter junction (Vbe) of about -6mV/K.
As can be seen from the Figure, voltage taps are taken from the base of transistor 2, namely feedback voltage (fb), the base of transistor 4, namely (-), and the emitter of transistor 4, namely (+), and these signals are fed to the feedback circuit 6 including operational amplifiers 20, 30, which effectively alters the feedback voltage (fb) such that a greater or lesser current flows through transistor 2 (and transistor 4) to maintain the voltage differential between Vbe2, being the base-emitter voltage of transistor 2, and V4, being the base-emitter voltage of the diode connected, reference transistor 4, substantially constant. The difference between the Vbe2 and Vbe4 is a reflection of the difference in temperature due to the temperature coefficient of the silicon junctions.
Given a means to hold the temperature difference constant, and with reference to a well-known formula (King's Law) relating heat dissipation and air velocity, an increase in the airflow across the sensors will require (and automatically cause, as a result of the feedback circuit) a current rise to restore the temperature difference. Again, a further mathematical relationship interrelates power (and hence current) directly to the square root of the air velocity given certain constraints on viscosity ("Reynolds Number").
Based on these mathematical relationships (all part of the prior art), it is possible to make a determination of the rate of flow past the transistor devices, but in practice, for this invention, it is only necessary to determine if there is flow or not, so the finer pints of the relationship do not matter, and no effort has been made in the theory or in the programmed microcontroller 10 to introduce any kind of linearization; only a quiescent no-flow "off' state is determined, together with an adjustable threshold for the "on" state.
The adjustment in the threshold state (i.e. the range of percentage deviation from the actual optimised current Cq) is achieved by means of the potentiometer arrangement shown in Figure iF, wherein in variable voltage 16 (offset") tap is taken across resistance R13 and supplied to the microcontroller 10, such supply also being indicated at 16.
As can be seen from the figure, transistor 2 is conventionally wired, and thus acts as a conventional transistor about 3 volts Vce (collector-emitter), and therefore gets hotter than the diode-connected, reference transistor 4 junction whilst carrying identical current.
A potentiometer RiO (in this example lOkO, but alternative values may be selected depending on various operating characteristics, in particular the pressure of the air supply) allows optimisation or fine tuning of the feedback circuit.
A further voltage tap () at 8 as taken across resistor R5 which provides an input for a microcontroller 10, in this embodiment a P1C12F675 chip programmed with at least a theoretically/experimentally determined optimum current Cq at which the circuit in question should operate under stable conditions. Additionally, the microcontroller 10 is programmed with a number of comparison routines which continually check the percentage deviation of the actual current (of which the voltage tap 8 is a measure) flowing through the pair of transistors from the optimised current, and depending on such deviation being greater or less than a predetermined, programmed amount, one, other or both of a pair of LEDs 12, 14, being respectively green and yellow, is illuminated extinguished, or caused to be illuminated intermittently in flashing manner.
As can be seen from Figure iD a further red LED is provided in series with an optically-isolated output signal coupler 22.
In operation, the sensor is first calibrated during "no-flow" or off' conditions.
Accordingly, the pressurised air supply is connected, through a manifold in which the sensor is positioned, to the pneumatically driven machine tool. If the current through the transistors, when the machine tool off, is less than 90% of Cq then the green LED flashes. If it is 90% or more of Cq then the green LED illuminates steadily. If the current is more than 110% then the yellow LED illuminates. From these two LEDs it is thus possible to quickly set the optimum working current in the range 90% to 110% of Cq by adjusting RiO, ideally a precision multi-turn potentiometer. It is to be noted that the sensor is inherently insensitive to ambient temperature changes as it works only on temperature differences.
The off/on threshold is then set by adjusting R13, which sets the threshold value relative to the 100% Cq value, for example 125% Cq, thus making the two adjustments more or less independent. The yellow LED gives visual re-assurance that low airflow is detected even if below the off/on threshold is reached, being a positive indicative of machine tool operation. Accordingly, in a particular preferred aspect of the invention, there is provided substantially independent means of calibrating the sensor, and providing or setting an on/off threshold value positively indicative of machine tool operation.
Other important aspects of the feedback circuit are the combination of C4 and R7 which form an integrator which ensures stability of the circuit, given that there is a timelag between change of current and change of temperature of the junctions. The value of R7 needs to be chosen for different physical types of transistors with different thermal time-constants. Op-amp 30 (ICib) and transistor Ti form an anti-lockup clamp circuit to prevent really large au-flows demanding excessive current and delaying recovery when the airflow stops.
In summary therefore, an air sensor comprising a blade on which a pair of semiconductor devices are surface-mounted and electrically connected in series is disclosed The blade is disposed in, sealed manner, an airflow path between a source of pressurised air and a pneumatically driven machine tool, and the sensor further comprises a feedback circuit, inputs of which are provided by the voltages across said semiconductor devices. The feedback circuit ensures that the differences between the voltages across each semiconductor devices, being indicative of the difference in the temperatures thereof, is maintained constant by varying the current through the devices as air flow past the devices changes. The feedback circuit further includes or is connected to a comparison means, together with visual indication means being one or more LEDs, the former making a comparison between the actual operating current flowing through said semiconductor devices and a predetermined, programmed or stored value indicative of an quiescent conditions, and depending on the result of said comparison, said comparison means causes illumination or extinction of one or more of the LEDs.

Claims (16)

1. An air sensor comprising a blade on which a pair of semiconductor devices are surface-mounted and electrically connected in series, said blade being disposed in the airflow path between a source of pressurised air and a pneumatically driven machine tool, and wherein said sensor further comprises a feedback circuit, inputs of which are provided by the voltages across said semiconductor devices, the difference between which is indicative of the difference in the temperatures thereof, there being applied a potential difference across said semiconductor devices and a current thus flowing therethrough, and said feedback circuit being capable of varying one of these parameters, the other being retained substantially constant so as to effectively retain the temperature difference between said semiconductor devices substantially constant, said feedback circuit further including a comparison means, together with visual indication means, which makes a comparison between the actual operating voltage applied to, or current flowing through, said semiconductor devices and a predetermined value indicative of an absence of airflow, and depending on the result of said comparison, said comparison means causes illumination or extinction of said visual indication means.
2. An air sensor according to claim 1 wherein a constant voltage is applied to the semiconductor devices and the feedback circuit causes a variation in the current therethrough to maintain the temperature difference therebetween substantially constant.
3. An air sensor according to any preceding claim wherein the blade is a separately detachable component from the feedback circuit, which is mounted on a separate printed circuit.
4. An air sensor according to any preceding claim wherein on or more of the semiconductor devices and the entire blade, is coated with a conformal silicone or other protective coating.
5. An air sensor according to any preceding claim wherein the semiconductor devices are transistors.
6. An air sensor according to claim 5 wherein one of the transistors is diode connected and acts as a ucoId reference temperature sensor, the alternate transistor operating conventionally, and electrically connected in series with said one transistor, inputs to said feedback circuit being derived from the base-emitter Voltages (Vbe) of each of said transistors such that the differential i\V is indicative of the temperature difference between the alternate, hotter transistor and reference transistor.
7. An air sensor according to any of claims 5 or 6 wherein the transistors are silicon NPN transistors
8. An air sensor according to any preceding claim wherein the comparison means is a microcontroller unit, and the visual indication means is one or more LEDs, said microcontroller being programmed to illuminate or extinguish said one or more LEDs when certain of the programmed conditions is satisfied or not satisfied, and further being connected to a voltage or current varying device which allows for adjustment of at least one output of said microcontroller.
9. An air sensor according to any claim 9 wherein said microcontroller is connected to and drives said one or more LEDs in a manner which allows a user, through non-illumination, intermittent illumination and/or continuous illumination, of said LEDs, to set the optimum working current for the feedback circuit.
10. An air sensor according to claim 8 or 9 wherein said microcontroller is connected to and drives a further LEDs in a manner which allows a user, and allows a userto set a machine tool operation threshold value which when exceeded, causes illumination of said further LED to enable a user to identify immediately if a machine tool is in operation.
11. An air sensor according to claim 9 and 10 wherein said microcontroller is capable of allowing the setting of optimum working current and machine tool operation threshold values substantially independently.
12. An air sensor according to any of claims 8-11 wherein the voltage or current varying device is a precision multi-turn potentiometer.
13. An air sensor according to any preceding claim wherein the visual indication means are three differently coloured LEDs.
14. An air sensor according to any preceding claim wherein the blade is mounted in a multi-way manifold block which is connected in series between the pressurised air supply and the hose which feeds the machine tool.
15. An air sensor according to any preceding claim wherein the blade is disposed with its broader surfaces axially aligned with the airflow such that the air flows over said broader surfaces on which said semiconductor components are surface mounted.
16. An air sensor according to any of claim 14 and 15 when dependent on 14 wherein a port of the manifold block is provided with a non-return valve and a common bleed valve.
GB0710236A 2007-05-30 2007-05-30 Airflow sensor Expired - Fee Related GB2449654B (en)

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GB2449654A true GB2449654A (en) 2008-12-03
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3061306A1 (en) * 2016-12-23 2018-06-29 Electricite De France SENSOR FOR MEASURING THE SPEED OF AN AIR FLOW, METHOD FOR MEASURING THE SPEED OF AN AIR FLOW USING THIS SENSOR AND INSTALLATION INCORPORATING SUCH A SENSOR
EP4060351A1 (en) * 2021-03-18 2022-09-21 Werme Patent AB Metering device for determining usage of a tool

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3898638A (en) * 1973-08-09 1975-08-05 Robert A Deane Differential temperature sensor system and improvements in a fluid flow detector
GB1488012A (en) * 1975-09-18 1977-10-05 Hawker Siddeley Dynamics Eng Mass flow transducers
US20030097875A1 (en) * 2001-11-26 2003-05-29 Honeywell International Inc. Airflow sensor, system and method for detecting airflow within an air handling system
WO2007014400A2 (en) * 2005-07-27 2007-02-01 Center For Multidisciplinary Studies Of The Belgrade University Three dimensional anemometer comprising thick film segmented thermistors

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3898638A (en) * 1973-08-09 1975-08-05 Robert A Deane Differential temperature sensor system and improvements in a fluid flow detector
GB1488012A (en) * 1975-09-18 1977-10-05 Hawker Siddeley Dynamics Eng Mass flow transducers
US20030097875A1 (en) * 2001-11-26 2003-05-29 Honeywell International Inc. Airflow sensor, system and method for detecting airflow within an air handling system
WO2007014400A2 (en) * 2005-07-27 2007-02-01 Center For Multidisciplinary Studies Of The Belgrade University Three dimensional anemometer comprising thick film segmented thermistors

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3061306A1 (en) * 2016-12-23 2018-06-29 Electricite De France SENSOR FOR MEASURING THE SPEED OF AN AIR FLOW, METHOD FOR MEASURING THE SPEED OF AN AIR FLOW USING THIS SENSOR AND INSTALLATION INCORPORATING SUCH A SENSOR
EP4060351A1 (en) * 2021-03-18 2022-09-21 Werme Patent AB Metering device for determining usage of a tool

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Publication number Publication date
GB2449654B (en) 2011-07-06
GB0710236D0 (en) 2007-07-11

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