GB2272296A - Medical airway temperature sensor - Google Patents
Medical airway temperature sensor Download PDFInfo
- Publication number
- GB2272296A GB2272296A GB9322664A GB9322664A GB2272296A GB 2272296 A GB2272296 A GB 2272296A GB 9322664 A GB9322664 A GB 9322664A GB 9322664 A GB9322664 A GB 9322664A GB 2272296 A GB2272296 A GB 2272296A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gases
- temperature
- temperature dependent
- dependent impedance
- 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.)
- Granted
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/087—Measuring breath flow
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/087—Measuring breath flow
- A61B5/0878—Measuring breath flow using temperature sensing means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
-
- 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
- G01F1/684—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
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
- G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K13/00—Thermometers specially adapted for specific purposes
- G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P13/00—Indicating or recording presence, absence, or direction, of movement
- G01P13/0006—Indicating or recording presence, absence, or direction, of movement of fluids or of granulous or powder-like substances
- G01P13/006—Indicating or recording presence, absence, or direction, of movement of fluids or of granulous or powder-like substances by using thermal variables
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Fluid Mechanics (AREA)
- Medical Informatics (AREA)
- Surgery (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Biophysics (AREA)
- Molecular Biology (AREA)
- Pathology (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Pulmonology (AREA)
- Physiology (AREA)
- Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
- Measuring Volume Flow (AREA)
Abstract
A sensor (1) used for sensing the flow rate and temperature of gases in a medical airway breathing circuit and designed for insertion into a breathing conduit includes a first thermistor (6) adapted to provide an indication of the gas flow rate and a further thermistor (7) to provide an indication of the gas temperature. The two thermistors are mounted on a projecting portion (5) of the sensor and connected to a cable (2) via a housing (4). The flow sensing thermistor (6) is protected by a portion (3) which carries the temperature sensing thermistor (7). A controller receives information from the thermistors (6, 7) and is able to determine therefrom an absence of gases flow or whether the sensor (1) has been removed from the gases flow, in addition to routine temperature monitoring. A safety feature of the sensor is the occasional operation of the flow rate sensing the thermistor (6) as a temperature sensing thermistor to check its integrity by comparing the temperature values sensed by the two thermistors (6, 7). <IMAGE>
Description
MEDICAL AIRWAY TEMPERATURE SENSOR
This invention relates to flow sensors and more particularly to sensors to detect gases flow rates and temperatures in medical applications.
In certain applications, for example, medical ventilator breathing circuits supplying gases to a patient, it is very important to determine whether or not a flow of gases is present. An absence of gases flow would indicate that the gases supply is not being delivered to the patient due perhaps to disconnection or occlusion of the breathing circuit. If a heated type humidifier were in the breathing circuit, supplying humidified gases to the patient, a lack of gases flow would necessitate the immediate cessation of heating since the temperature of the static gases would otherwise increase to a level which could harm the patient, especially should the gases flow be recommenced.
A second important parameter in gases flows, especially in certain medical applications, is the temperature of the gases. When the gases are in the breathing circuit of a heated type humidifier, temperature control is particularly important and in some cases warrants the inclusion of more than one temperature probe such as a temperature probe near the humidifier and another, near the patient, connected to the breathing tube. An example of a humidification system which utilises temperature probes positioned in the breathing circuit is disclosed in our prior US Patent No.
4,708,831. In some existing humidification systems, if a temperature probe was removed, malfunctioned or was inadvertently installed incorrectly, a low temperature would be detected and the control system would then increase the heat to the humidifying apparatus and thus the temperature of the humidified gases would also increase. This harmful situation could be obviated by incorporating a flow sensor with the temperature sensor so that if the aforementioned situation were to arise, no gases flow would be detected and the humidifier could react accordingly. There are many prior art gas flow sensors available which are usually large, difficult to clean and are expensive. Many prior art flow sensing devices are not suitable to the sterile and demanding clinical environment especially within a humidifier breathing circuit which is necessarily warm and moist. The principle of measuring heat loss or heat transfer to a gases stream to determine the flow rate is known. Some prior art flow sensors have utilised thermistors (temperature dependent impedance) however they have usually been too delicate, sometimes necessitating housing within a protective shield thus maIling them unacceptable obtrusions into the breathing circuit and also causing other difficulties including cleaning.
It is, therefore, an object of the present invention to provide a flow sensor which goes some way towards overcoming the above disadvantages or which will at least provide the public with a useful choice.
Accordingly, in one aspect the invention consists in apparatus for sensing gases flow and gases temperature of a moving gases stream comprising:
a sensor having a body with a projecting portion for placement within a conduit in which gases are flowing,
said projecting portion includes two temperature dependent impedances, a first temperature dependent impedance for measuring gases temperature and a second temperature dependent impedance for measuring gases flow.
In a second aspect the invention consists in a method of determining the flow rate and temperature of gases in a moving gases stream using a temperature dependent impedance placed in- said-gases stream, said method comprising the steps of:
(i) supplying a substantially constant electrical current to said temperature dependent impedance,
(ii) detecting the energy dissipated by said temperature dependent impedance to said gases in said gases stream, (iii) from the energy dissipated, establishing said flow rate,
(iv) ceasing the supply of current to said temperature dependent impedance for a predetermined period to allow said temperature dependent impedance to cool to the temperature of said gases stream, and
(v) supplying a substantially constant voltage to said temperature dependent impedance to determine the temperature of said gases in said gases stream.
In a further aspect the invention consists in a controller for controlling humidifying apparatus of the type used to supply humidified gases to a patient, said controller comprising:
means for generating a substantially constant source of current or a substantially constant source of voltage for supply to a first temperature dependent impedance,
means to alternately supply said constant current source or said constant voltage source to said first temperature dependent impedance to obtain measurements of said gases temperature and said gases flow, and
a timer to selectively allow a predetermined period of time to elapse between supplying said constant current to said first temperature dependent impedance and said constant voltage.
The invention consists in the foregoing and also envisages constructions of which the following gives examples.
One preferred form of the invention will now be described with reference to the accompanying drawings in which;
Figure 1 is a side elevation of a flow sensor incorporating the present invention,
Figure 2 is a front elevation of the flow sensor of Figure 1 showing the probes of the present invention,
Figure 3 is a simplified circuit diagram of a flow rate sensing thermistor arrangement according to the present invention,
Figure 4 is a simplified circuit diagram of the temperature sensing thermistor arrangement according to the present invention, and
Figure 5 is a circuit block diagram illustrating the circuit used to enable the flow sensing thermistor of the present invention to be also used as a temperature sensor.
With reference to Figure 1, a flow sensor generally referenced 1 for measuring the flow of gases in, for example, a humidifier breathing circuit, includes a plastic insulated connecting cable 2 surrounded by a flexible protective sheath 9.
A housing 4 to which the protective sheath 9 is connected and into which cable 2 enters is also shown further connected to a protruding member 5. A sensor housing and protector 3 is attached to the end of the protruding member 5. By referring to
Figure 2 it can be seen that the sensor housing and protector 3 is of a substantially "U" shape so as to allow for a first temperature dependent impedance in the form of a thermistor 6 to be accommodated and protected. A second temperature dependent impedance in the form of a thermistor 7 is incorporated at the end of the sensor housing and protector 3 while both the first and second thermistors are electrically connected to wires within the cable 2 so that signals developed by the thermistors may be sent to a controller (not shown). The flow sensor 1 has the basic shape and dimensions of a presently available temperature probe, thus facilitating the use of the present invention in currently used breathing circuits.
In use, the first thermistor 6 and second thermistor 7 must be in the flow of a fluid, for example, gases in a humidifier breathing circuit supplying humidified gases to a patient in a hospitaL The flow sensor 1 may be connected to a breathing conduit between the patient and a humidifier by pushing the protruding member S through a hole in the conduit, the hole being the same or similar diameter as the protruding member so that a substantially gas tight connection is made between the conduit and the protruding member. The sensor may be fastened into place or may rely on friction between the protruding member 5 and the conduit to hold it to the conduit with the underside 8 of the housing 4 in close proximity to the surface of the conduit.
In such a position, the first thermistor 6 and second thermistor 7 are placed within the fluid flow through the conduit.
The first thermistor 6 is used to sense the rate of flow of gases in the conduit by an electrical circuit such as that shown in Figure 3. Referring to Figure 3, in order to determine the rate of flow of the gases, the thermistor 6 is provided with a source of constant current 11 via input voltage 10 (Vh,) supplied by wires within cable 2 such that the constant current is forced to flow through thermistor 6. As the thermistor is an energy dissipating circuit element, heat is produced, as shown by arrows 14, and the thermistor 6 will be heated above ambient temperature, that is, it will become warm to the touch The thermistor characteristics are well known and are such that the resistance of the device will decrease with an increase in temperature, therefore, the voltage at node 12 with respect to ground will decrease with the drop in resistance. The operating temperature of thermistor 6 should be kept above that of the gases in the conduit in order that heat may be transferred to the gases. As the thermistor resistance varies (depending on the flow rate and heat transferred to the gases) so will the voltage at node 12 such that the more heat dissipated by the thermistor to the gases now, the cooler the thermistor will become and, therefore, the higher its resistance and the voltage at node 12 will become.
Therefore, it can be seen that the node 12 voltage is indicative of heat transferred to the gases and this can then easily be calibrated to give a flow rate.
The second thermistor 7 is configured so as to provide a signal indicative of the temperature of the gases flow. This is achieved by an electrical circuit such as that shown in Figure 4. Referring to Figure 4, a known constant voltage Vi, is applied at node 20 so that a current will flow through the resistor 21 and thermistor 7 dependent on the total series resistance of the two components. This total resistance will be governed by the temperature of the thermistor 7 such that for low temperatures, the resistance of thermistor 7 will be high and therefore the voltage at node 22 (Vaut) will approach VIII. For higher temperatures however, the voltage at node 22 will approach zero as the thermistor resistance decreases. It can, therefore, be seen that the range of output voltages at node 22 may be calibrated to give temperature values for the gases flow. These temperature values may then be used to compensate the first thermistor 6 for variations in temperature to give a more accurate flow rate reading.
A method by which the now- rate sensing thermistor 6 may be used to check on the integrity of the temperature sensing thermistor 7 will now be described with reference to Figure 5. An electrical switch 34 may be placed in one of two positions 35 or 36. If the switch were to be in position 35 (as shown) a circuit would be formed as previously dessnbed with reference to Figure 3 with an output voltage at node 12 corresponding to the heat transferred to the gases. This signal is then input to a buffer/amplifier 32 which has a high input impedance so as not to load the circuit.
The output of the buffer/amplifier 32 is connected to an input of Analogue to Digital
Convertor (ADC) 31 which converts the voltage input to a corresponding binary digital form recognisable by microprocessor 30. The microprocessor 30 then calibrates this voltage within a software program to calculate the flow rate of the gases.
Alternatively, if the switch 34 were to be in position 36, the thermistor 6 would be in a circuit as previously described with reference to Figure 4. After a predetermined cooling down period set by microprocessor 30 to allow the temperature of thermistor 6 to match that of the gases, the voltage at node 22, corresponding to the temperature of thermistor 6, is input to buffer/amplifier 33 which also has a high input impedance. The output of buffer/amplifier 33 is detected by ADC 31 which converts the voltage to a corresponding binary digital form recognisable by microprocessor 30. The microprocessor 30 utilises the ADC output value in its software program to determine the temperature.
The software program in the microprocessor 30 also includes steps of on occasion sending a signal to the switch 34 via path 37 to alter the position of the electrical switch 34 from the normal position 35 to a temporary position 36 so that thermistor 6 may be used to test the integrity of thermistor 7 which preferably constantly measures temperature.
When compared to a prior art temperature sensor without a flow sensor, the present invention, at least in the preferred form, has the advantage that it can detect when the sensor is removed from the gases stream. This may be achieved as a lack of gases flow will be registered. A prior art temperature sensor without flow sensor may attempt to increase the temperature of the humidified gases if this situation were to arise which could harm the patient, whereas the present invention would automatically put itself into a safe state and preferably raise an alarm. Another advantage of the present invention is. the incorporation of a back up temperature sensor by way of thermistor 6 in an effort to increase the overall reliability of the sensor.
Claims (14)
1. Apparatus for sensing gases flow and gases temperature of a moving gases stream comprising:
a sensor having a body with a projecting portion for placement within a conduit in which gases are flowing,
said projecting portion includes two temperature dependent impedances, a first temperature dependent impedance for measuring gases temperature and a second temperature dependent impedance for measuring gases flow.
2. Apparatus as claimed in claim 1 wherein a protection member is also provided adjacent to one of said first or said second temperature dependent impedances for physical protection of said first or second temperature dependent impedance.
3. Apparatus as claimed in claim 2 wherein the temperature dependent impedance which is not protected by said protection member is located on a portion of said protection member.
4. Apparatus as claimed in any one of the preceding claims wherein said apparatus also includes a controller which provides electrical energy to said first and second temperature dependent impedances to obtain electrical signals from said temperature dependent impedances which signals are indicative of said gases temperature and said gases flow, said controller periodically using said second temperature dependent impedance to measure the temperature of said gases temperature as well as said gases flow and comparing said gases temperature determined by said second temperature dependent impedance with the gases temperature determined by said first temperature dependent impedance.
5. Apparatus for sensing gases flow and gases temperature of a moving gases stream substantially as hereinbefore described with reference to the accompanying drawings.
6. A method of determining the flow rate and temperature of gases in a moving gases stream using a temperature dependent impedance placed in said gases stream, said method comprising the steps of:
(i) supplying a substantially constant electrical current to said temperature dependent impedance,
,.
(ii) detecting the energy dissipated by said temperature dependent impedance to said gases in said gases stream,
(iii) from the energy dissipated, establishing said flow rate,
(iv) ceasing the supply of current to said temperature dependent impedance for a predetermined period to allow said temperature dependent impedance to cool to the temperature of said gases stream, and
(v) supplying a substantially constant voltage to said temperature dependent impedance to determine the temperature of said gases in said gases stream.
7. A method as claimed in claim 6 wherein said method includes the step of comparing the temperature of said gases with a temperature determined by a further temperature dependent impedance positioned in the gases flow.
8. A method as claimed in either claim 6 or claim 7 wherein said method includes the step of repeating the preceding steps.
9. A method of determining the flow rate and temperature of gases in a moving gases stream using a temperature dependent impedance placed in said gases stream substantially as hereinbefore described with reference to the accompanying drawings.
10. A controller for controlling humidifying apparatus of the type used to supply humidified gases to a patient, said controller comprising:
means for generating a substantially constant source of current or a substantially constant source of voltage for supply to a first temperature dependent impedance,
means to alternately supply said constant current source or said constant voltage source to said first temperature dependent impedance to obtain measurements of said gases temperature and said gases flow, and
a timer to selectively allow a predetermined period of time to elapse between supplying said constant current to said first temperature dependent impedance and said constant voltage.
11. A controller as claimed in claim 10 wherein said controller supplies a substantially constant source of voltage to a second temperature dependent impedance positioned in the gases flow.
12. A controller as claimed in either claim 10 or claim 11 wherein comparing means are provided to compare said gases temperature determined by said first temperature dependent impedance with a gases temperature determined by said second temperature dependent impedance.
13. A controller for controlling humidifying apparatus of the type used to supply humidified gases to a patient substantially as hereinbefore described with reference to Figures 3 to 5 of the accompanying drawings.
14. Any novel feature or combination of features described herein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9616513A GB2301440B (en) | 1992-11-04 | 1993-11-03 | Medical airway temperature sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NZ24500992 | 1992-11-04 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9322664D0 GB9322664D0 (en) | 1993-12-22 |
| GB2272296A true GB2272296A (en) | 1994-05-11 |
| GB2272296B GB2272296B (en) | 1997-04-16 |
Family
ID=19924171
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9322664A Expired - Lifetime GB2272296B (en) | 1992-11-04 | 1993-11-03 | Medical airway temperature sensor |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2272296B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996031759A2 (en) * | 1995-04-03 | 1996-10-10 | Ifm Electronic Gmbh | Heat transmission monitoring and/or measuring apparatus |
| EP0829727A3 (en) * | 1996-09-06 | 1998-09-30 | De' Longhi S.P.A. | Method and device for detecting a gaseous flow |
| EP1374940A2 (en) | 1997-06-17 | 2004-01-02 | Fisher & Paykel Healthcare Limited | Respiratory humidification system |
| DE102008024123B3 (en) * | 2008-05-17 | 2009-11-19 | Dräger Medical AG & Co. KG | Connection component for a breathing tube with a sensor for measuring the gas flow |
| ITCO20120067A1 (en) * | 2012-12-20 | 2014-06-21 | Nuovo Pignone Srl | MEASUREMENT OF TOTAL PRESSURE AND TOTAL TEMPERATURE IN THE CONDITION OF HUMID GAS |
| USD742507S1 (en) | 2013-01-22 | 2015-11-03 | Intersurgical Ag | Sensor with connector for resiratory circuit |
| US10207073B2 (en) | 2011-02-21 | 2019-02-19 | Intersurgical Ag | Respiratory apparatus |
| US20220163404A1 (en) * | 2020-04-17 | 2022-05-26 | Telligent Metrics LLC | Thermistor based respiration measurement |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2017326905B2 (en) * | 2016-09-16 | 2023-04-27 | Fisher & Paykel Healthcare Limited | Thermistor flow sensor having multiple temperature points |
| CN112461294A (en) * | 2020-09-14 | 2021-03-09 | 湖南明康中锦医疗科技发展有限公司 | Temperature and humidity sensor mounting structure and breathing support equipment |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4304129A (en) * | 1978-11-13 | 1981-12-08 | Nippon Soken, Inc. | Gas flow measuring apparatus |
| GB2143951A (en) * | 1983-07-20 | 1985-02-20 | Bosch Gmbh Robert | Flow rate measuring means |
| US4709581A (en) * | 1984-09-07 | 1987-12-01 | Hitachi, Ltd. | Air flow meter |
| US4805452A (en) * | 1985-12-04 | 1989-02-21 | Degusa Aktiengesellschaft | Device for the thermal measurement of the mass flow gases and liquids |
| US4911008A (en) * | 1988-10-03 | 1990-03-27 | Allied-Signal Inc. | Hot film anemometer |
| US5060511A (en) * | 1989-03-31 | 1991-10-29 | Aisan Kogyo Kabushiki Kaisha | Intake air quantity measuring apparatus |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4335605A (en) * | 1980-05-14 | 1982-06-22 | Thermal Instrument Company | Mass flow meter |
| US4501145A (en) * | 1981-07-13 | 1985-02-26 | Battelle Memorial Institute | Immersion thermal exchange parameter determination |
| SE466820B (en) * | 1990-07-17 | 1992-04-06 | Bengt Noren | PROCEDURE AND DEVICE FOR FLOW SPEED Saturation |
-
1993
- 1993-11-03 GB GB9322664A patent/GB2272296B/en not_active Expired - Lifetime
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4304129A (en) * | 1978-11-13 | 1981-12-08 | Nippon Soken, Inc. | Gas flow measuring apparatus |
| GB2143951A (en) * | 1983-07-20 | 1985-02-20 | Bosch Gmbh Robert | Flow rate measuring means |
| US4709581A (en) * | 1984-09-07 | 1987-12-01 | Hitachi, Ltd. | Air flow meter |
| US4805452A (en) * | 1985-12-04 | 1989-02-21 | Degusa Aktiengesellschaft | Device for the thermal measurement of the mass flow gases and liquids |
| US4911008A (en) * | 1988-10-03 | 1990-03-27 | Allied-Signal Inc. | Hot film anemometer |
| US5060511A (en) * | 1989-03-31 | 1991-10-29 | Aisan Kogyo Kabushiki Kaisha | Intake air quantity measuring apparatus |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996031759A2 (en) * | 1995-04-03 | 1996-10-10 | Ifm Electronic Gmbh | Heat transmission monitoring and/or measuring apparatus |
| WO1996031759A3 (en) * | 1995-04-03 | 1996-11-07 | Ifm Electronic Gmbh | Heat transmission monitoring and/or measuring apparatus |
| US5848094A (en) * | 1995-04-03 | 1998-12-08 | I F M Electronic Gmbh | Heat transmission monitoring and/or measuring apparatus |
| EP0829727A3 (en) * | 1996-09-06 | 1998-09-30 | De' Longhi S.P.A. | Method and device for detecting a gaseous flow |
| EP1374940A2 (en) | 1997-06-17 | 2004-01-02 | Fisher & Paykel Healthcare Limited | Respiratory humidification system |
| US8171811B2 (en) | 2008-05-17 | 2012-05-08 | Dräger Medical GmbH | Connecting component for a breathing tube with a sensor for measuring the gas flow |
| DE102008024123B3 (en) * | 2008-05-17 | 2009-11-19 | Dräger Medical AG & Co. KG | Connection component for a breathing tube with a sensor for measuring the gas flow |
| US10207073B2 (en) | 2011-02-21 | 2019-02-19 | Intersurgical Ag | Respiratory apparatus |
| ITCO20120067A1 (en) * | 2012-12-20 | 2014-06-21 | Nuovo Pignone Srl | MEASUREMENT OF TOTAL PRESSURE AND TOTAL TEMPERATURE IN THE CONDITION OF HUMID GAS |
| WO2014095711A1 (en) * | 2012-12-20 | 2014-06-26 | Nuovo Pignone Srl | Total pressure and total temperature measurement in wet gas condition |
| US9846098B2 (en) | 2012-12-20 | 2017-12-19 | Nuovo Pignone Srl | Total pressure and total temperature measurement in wet gas condition |
| USD742507S1 (en) | 2013-01-22 | 2015-11-03 | Intersurgical Ag | Sensor with connector for resiratory circuit |
| USD792585S1 (en) | 2013-01-22 | 2017-07-18 | Intersurgical Ag | Sensor for respiratory circuit |
| US20220163404A1 (en) * | 2020-04-17 | 2022-05-26 | Telligent Metrics LLC | Thermistor based respiration measurement |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2272296B (en) | 1997-04-16 |
| GB9322664D0 (en) | 1993-12-22 |
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| Date | Code | Title | Description |
|---|---|---|---|
| PE20 | Patent expired after termination of 20 years |
Expiry date: 20131102 |