METHOD AND APPARATUS FOR DETERMINING THE FLOW PARAMETERS OF A STREAMING MEDIUM

• US 20100095782A1
• Filed: 12/05/2008
• Published: 04/22/2010
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Uscom Ltd.
• Original Assignee: Uscom Ltd.
• Inventors: Rozsnyik, Zoltan, Ferencz, György
• Granted Patent: US 10,031,011 B2
• Time in Patent Office: Days
• US Class Current: 73/861.28
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01F 1/662 Constructional details
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
• CPC Class Codes: G01F 15/14 Casings, e.g. of special material
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

According to the method longitudinal waves are generated in a transducer used only as a transmitter connected from outside to a conduit. These waves are transmitted along two diagonal paths through the streaming medium in an upstream and a downstream direction, and received by two transducers used only as receivers which are located in a diagonal upstream and downstream position and on an opposite side relative to the transducer used as a transmitter, also connected to the conduit. A transit time value of the waves between the transducer used as a transmitter and each of the transducers used as receivers is determined. A difference value on the basis of the determined transit time values is generated and the flow parameters are determined on the basis of said difference value. This measuring method is highly independent of the propagation velocity of the wave in the medium streaming in the conduit therefore also independent of the temperature and humidity of a gaseous medium. An apparatus and a conduit for use in the apparatus for performing the method is also suggested. The conduit used in the apparatus comprises a first location for receiving a transmitter in a middle region of the measuring area and two second locations for receiving receivers in a border region of the measuring area opposite to the first location. The wall of the conduit is dimensioned so that the longitudinal waves can pass through it with minimal loss and maximum efficiency. The inner wall of the conduit forms a uniform and continuos surface for the transmission of the longitudinal waves between the transmitter and the receivers and for blocking the passage of any organic or inorganic material. In medical applications the apparatus and its housing is configured to receive, hold and release a sterile conduit.

Claims

1. A method for determining the flow parameters of a streaming gas in a conduit for medical applications the method comprising the steps of:

generating longitudinal waves inside the conduit with a transducer,

transmitting said longitudinal waves in two different cross directions relative to the streaming direction (upstream and downstream direction) through the conduit,

receiving said waves with transducers,

determining transit time values of the waves between the transducer used as a transmitter and the transducers used as receivers,

generating a difference value on the basis of the determined transit time values, and

determining the flow parameters of the streaming gas on the basis of said difference value,

characterized in, the method further includes the steps of;

determining a first pair of transit time values of the waves between the transducer used as a transmitter and the transducers used as receivers,

determining an approximate flow rate of the streaming gas on the basis of a difference between the first pair of transit time values and the transit times corresponding to a zero flow rate,

determining a time shift value necessary for the streaming gas to propagate from a first wave transmission path to a second wave transmission path,

determining a second pair of transit time values of the waves between the transducer used as a transmitter and the transducers used as receivers with a delay between the upstream and downstream transmission path transit time measurements, the delay being determined by said time shift value, and

determining a more accurate flow rate of the streaming gas on the basis of a difference between the second pair of transit time values.

2. The method of claim 1, characterized in that the transit times are determined by

determining transit times between the transducer used as a transmitter and the transducers used as receivers under normal conditions when the flow rate is zero,

measuring a phase shift of the zero crossing of a corresponding rising edge of the received signal,

calculating a time difference corresponding to said phase shifting, and

adding the time difference to the transit time under zero flow condition.

3. The method of claim 1, characterized in that the longitudinal waves generated by the transducer used as a transmitter are in the form of wave packages separated from each other by a period sufficiently long for identifying the appropriate pulse packages and the transit times are determined by measuring the time between a selected point of the transmitted wave package and a corresponding point of the same received wave package.

4. The method of claim 3, characterized in that subsequent wave packages following each other are shifted in phase with respect to each other wherein the phase shift is selected randomly between a minimum and a maximum value, for inhibiting the forming of standing waves inside the conduit.

5. The method of claim 1, characterized in that a zero crossing is used for determining the transit time values after the amplitude of the received signal has exceeded a predetermined comparator level when the zero crossing is inside a time window determined by minimum and maximum streaming conditions.

6. The method of claim 1, characterized in that the transit times between the transducer used as a transmitter and the transducers used as receivers are determined under zero flow condition wherein the transducers used as receivers are located symmetrically relative to the transducer used as a transmitter and if a difference between the two transit times is detected, an offset value is determined and all subsequent measured values are corrected on the basis of the offset value.

7. The method of claim 1, characterized in that the transit times between the transducer used as a transmitter and the transducers used as receivers are determined under zero flow condition, wherein the transducers used as receivers are located asymmetrically relative to the transducer used as a transmitter and if a difference between a calculated or nominal position and an actual position of the transducer used as a transmitter can be detected, a correction value is determined and all subsequent measured values are modified with the correction value.

8. The method of claim 1, characterized in that the flow rate value of the streaming gas in a low flow rate range is corrected by a predetermined value selected on the basis of an analysis of a selected package of the received waves.

17. An ultrasonic spirometer, especially for carrying out the method of claim 1, comprising a housing with

a transducer configured as a transmitter for generating longitudinal waves inside a conduit and for transmitting said longitudinal waves in two different cross directions relative to the streaming direction (upstream and downstream direction) through the conduit,

two transducers configured as receivers for receiving said waves positioned diagonally in an upstream and downstream position relative to the transmitter,

means for determining transit time values of the waves between the transducer configured as a transmitter and the transducers configured as receivers,

means for generating a difference values on the basis of the determined transit time values, and

means for determining the flow parameters on the basis of said difference values, characterized in, that it comprises a conduit of any one of claim 9.

18. The spirometer of claim 17, characterized in that the housing and the conduit are configured so that the conduit is removable or changeable.

19. The spirometer of claim 17, characterized in that the conduit is configured so that it is an integral part of the housing.

20. The spirometer of claim 17, characterized in that the housing enclosing the conduit is configured to be opened and closed for removing or changing the conduit and further comprising

means for calibrating the spirometer in a zero flow rate condition and a predetermined flow rate condition.

9. A conduit for use in a medical apparatus for determining the flow parameters of a gas streaming in the conduit, the conduit comprising

open end sections and a measuring section between end sections of the conduit,

a first location in a middle region of the measuring section for receiving a transducer used for generating longitudinal waves inside the conduit and for transmitting said longitudinal waves in two different cross directions relative to the streaming direction (upstream and downstream direction) through the conduit, and

two second locations in a border region of the measuring section opposite to the first location for receiving transducers used for receiving said waves,

characterized in, that

the end sections have a substantially circular cross section and

the measuring section has a substantially rectangular cross section with narrow side walls and wide side walls, wherein

the transducers are connected to the narrow side walls, and the inner wall of the conduit forms a continuous surface with respect to the streaming gas.

10. The conduit of claim 9, comprising transducers connected to the conduit in a permanent way.

11. The conduit of claim 9, comprising transducers connected to the conduit in a releasable way.

12. The conduit of claim 9, characterized in that the layer in front of the active elements of the transducers are wave impedance coupled to the streaming gas.

13. The conduit of claim 9, characterized in that the transducers are sinked into the wall of the conduit and the inner surface of the conduit is covered with a wave impedance coupling foil.

14. The conduit of claim 9, characterized in that the transducers are located in an open end hole with a wear plate on the inside surface.

15. The conduit of claim 14, characterized in that the wear plate is made of PTFE.

16. The conduit of claim 9, characterized in that the wall of the conduit is provided with wave propagation inhibiting elements in proximity of the transducers.

21-25. -25. (canceled)