In-line fluid monitor system and method

• US 5,260,665 A
• Filed: 04/30/1991
• Issued: 11/09/1993
• Est. Priority Date: 04/30/1991
• Status: Expired due to Term

• Current Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Original Assignee: Ivax Corporation (Teva Pharmaceutical Industries, Ltd.)
• Inventors: Zublin, Kurt E., Bell, Marl J., Goldberg, Jack
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): REGAN, MAURA K
• Application Number:
  US07/693,357
• Time in Patent Office: 924 Days
• Field of Search: 324/636, 324/639, 73/19.1, 73/19.05, 73/61 R, 73/204.23, 604/50, 604/65, 128/653.1, 333/230, 333/246
• US Class Current: 324/636
• CPC Class Codes: G01L 9/0001 Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means G01L9/0026, G01L9/0033, G01L9/0082, G01L9/0089, G01L9/0091 take precedence
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence

Abstract

A non-invasive, in-line fluid monitor includes a segment of fluid line disposed such that it and the fluid within become a part of the dielectric loading on an energized electromagnetic sensor device. Perturbations of the dielectric loading on the sensor device are monitored to determine certain fluid properties, such as pressure, composition, and the presence of air. The fluid line segment disposed through the electromagnetic sensor may be compliant and thus changes size in response to fluid pressure, altering the volume of the fluid line segment tin the cavity and altering the dielectric loading on the cavity. In one embodiment, a resonant cavity is used to encompass the segment of fluid line and a processor is used to compare changes in the resonant characteristics of the cavity to predetermined data to determine the properties of the fluid. In an alternative embodiment, a transmission device such as a delay line is utilized as the sensor element, and in another embodiment, a microstrip resonator is utilized as the sensor element. In yet another embodiment incorporating a means of determining the volumetric fluid flow rate, the size of air bubbles in the fluid is assessed.

Claims

1. An apparatus for monitoring fluid in a fluid line, the apparatus comprising:

a compliant fluid line segment coupled to the fluid line such that the fluid flows through the segment;

a dielectrically loaded electromagnetic sensing device coupled to the compliant segment such that the segment and fluid therein provide dielectric loading on the sensing device, the sensing device providing a sensor signal representative of the dielectric loading;

a flow data source which provides a flow signal representative of the volumetric flow rate of the fluid in the fluid line; and

a processor, having predetermined gas data representative of a gas in the fluid, which receives the sensor signal from the sensing device, provides a loading signal representative of the dielectric loading, compares the loading signal to the predetermined gas data to detect the presence of the gas and upon detecting the gas, determines the time period that the sensing device detects the gas and processes the detection time period with the flow signal and provides a signal indicative of the size of the gas bubble.

2. The apparatus of claim 1 wherein:

the predetermined data comprises data representing a solute in the fluid; and

the second processor compares the loading signal to the predetermined solute data and provides a signal representative of the concentration of the solute in the fluid.

3. An apparatus for monitoring fluid in a fluid line, the apparatus comprising:

a dielectrically loaded resonant electromagnetic sensing device coupled to a segment of the fluid line such that the segment and fluid therein form part of the dielectric loading on the sensing device, the sensing device provides a sensor signal representative of the dielectric loading;

a flow data source which provides a flow signal representative of the volumetric flow rate of the fluid in the fluid line;

a processor, having predetermined gas data representative of a gas in the fluid, which receives the sensor signal from the sensing device, provides a loading signal representative of the dielectric loading, compares the loading signal to the predetermined gas data to detect the presence of the gas and upon detecting the gas, determines the time period that the sensing device detected the gas, processes the detection time period with the flow signal and provides a signal indicative of the size of the gas bubble.

4. The apparatus of claim 3 wherein the dielectrically loaded resonant device comprises a resonant cavity having an electric field and a focusing post which focuses the electric field onto the segment of fluid line such that the segment provides a substantial part of the dielectric loading of the cavity.

5. The apparatus of claim 3 wherein:

the resonant device comprises a microstrip resonator;

the fluid line segment is disposed to provide dielectric loading to the microstrip resonator; and

the sensor signal represents the dielectric loading of the microstrip resonator.

6. The apparatus of claim 3 wherein:

the resonant device comprises a stripline resonator;

the fluid line segment is disposed to provide dielectric loading to the stripline resonator; and

the sensor signal represents the dielectric loading of the stripline resonator.

7. An apparatus for monitoring fluid in a fluid line, the apparatus comprising:

a dielectrically loaded electromagnetic sensing device having a planar structure and coupled to a segment of the fluid line such that the segment and fluid therein provide dielectric loading on the sensing device, the sensing device provides a sensor signal representative of the dielectric loading;

a processor having predetermined gas data representative of a gas in the fluid, which receives the sensor signal from the sensing device, provides a loading signal representative of the dielectric loading, compares the loading signal to the predetermined gas data to detect the presence of the gas and provides a signal indicative of the gas detection.

8. The apparatus of claim 7 wherein the planar sensing device comprises a resonant device, a resonant characteristic of which varies in response to the dielectric loading;

the segment is disposed to provide dielectric loading to the resonant device;

the sensor signal is responsive to the resonant characteristic; and

the processor provides the loading signal in response to the resonant characteristic.

9. The apparatus of claim 8 wherein:

the planar sensing device comprises a microstrip resonator;

the segment is disposed to provide dielectric loading to the microstrip resonator; and

the sensor signal represents the dielectric loading of the microstrip resonator.

10. The apparatus of claim 8 wherein:

the planar sensing device comprises a stripline resonator;

the segment is disposed to provide dielectric loading to the stripline resonator; and

the sensor signal represents the dielectric loading of the stripline resonator.

11. The apparatus of claim 7 wherein:

the planar sensing device comprises a transmission device, the delay through which varies in response to the dielectric loading;

the segment is disposed to provide dielectric loading to the transmission device;

the sensor signal is responsive to the delay through the transmission device; and

the processor provides the loading signal in response to the delay.

12. A method of monitoring fluid in a fluid line, comprising the steps of:

forming a segment of the fluid line of complaint material;

sensing the volumetric flow rate of the fluid in the fluid line and providing a flow signal representative of the rate;

disposing the compliant segment such that it and the fluid therein provide dielectric loading on a sensing device;

sensing the dielectric loading of the sensing device;

providing a loading signal which is representative of the sensed dielectric loading of the sensing device;

comparing the loading signal to predetermined gas data which is representative of a gas in the fluid to detect the presence of the gas and upon detecting the gas, processing the time period that the gas is detected with the flow signal and providing a signal indicative of the size of the gas bubble passing through the fluid line in response to said comparison.

13. A method of monitoring fluid in a fluid line, comprising the steps of:

disposing a segment of the fluid line such that it and the fluid therein provide dielectric loading on a resonant electromagnetic sensing device, a resonant characteristic of which varies in response to the dielectric loading;

sensing the resonant characteristic of the sensing device;

providing a loading signal which is representative of the sensed resonant characteristic of the sensing device;

sensing the volumetric flow rate of the fluid in the fluid line and providing a flow signal representative of the rate; and

comparing the loading signal to predetermined gas data which is representative of a gas in the fluid, to detect the presence of the gas and upon detecting the gas, processing the time period that the gas is detected with the flow signal and providing a signal indicative of the size of the gas bubble passing through the fluid line in response to the comparison.

14. The method of claim 13 further comprising the steps of:

providing a resonant cavity as the resonant device;

forming an electric field in the cavity; and

focusing the electric field onto the compliant segment of fluid line such that the segment forms a substantial part of the dielectric loading of the sensing device.

15. The method of claim 13 further comprising the steps of:

providing a microstrip resonator as the resonant device;

disposing the fluid line segment to provide dielectric loading to the microstrip resonator;

monitoring a resonant characteristic of the microstrip resonator; and

providing the loading signal in response to the resonant characteristic.

16. The method of claim 13 further comprising the steps of:

providing a stripline resonator as the resonant device;

disposing the fluid line segment to provide dielectric loading to the stripline resonator;

monitoring a resonant characteristic of the stripline resonator; and

providing the loading signal in response to the resonant characteristic.

17. An apparatus for monitoring fluid in a fluid line, the apparatus comprising:

a dielectrically loaded transmission electromagnetic sensing device coupled to a segment of the fluid line such that the segment and fluid therein form part of the dielectric loading on the sensing device, the sensing device having a delay which varies in response to the dielectric loading and provides a sensor signal representative of the delay;

a flow data source which provides a flow signal representative of the volumetric flow rate of the fluid in the fluid line;

a processor, having predetermined gas data representative of a gas in the fluid, which receives the sensor signal from the sensing device and in response to the delay, provides a loading signal representative of the dielectric loading, compares the loading signal to the predetermined gas data to detect the presence of the gas and upon detecting the gas, determines the time period that the sensing device detects the gas, processes the detection time period with the flow signal and provides a signal indicative of the size of the gas bubble.

18. A method of monitoring fluid in a fluid line, comprising the steps of:

disposing a segment of the fluid line such that it and the fluid therein provide dielectric loading on a transmission electromagnetic sensing device, the delay through which varies in response to the dielectric loading;

sensing the delay of the sensing device;

providing a loading signal which is representative of the sensed delay of the sensing device;

sensing the volumetric flow rate of the fluid in the fluid line and providing a flow signal representative of the rate; and

comparing the loading signal to predetermined gas data which is representative of a gas in the fluid, to detect the presence of the gas and upon detecting the gas, processing the time period that the gas is detected with the flow signal and providing a signal indicative of the size of the gas bubble passing through the fluid line in response to the comparison.