Electromagnetic
Download
1 / 38

Electromagnetic Blood Flow Meter Dr. Erdem Topsakal, Advisor Br - PowerPoint PPT Presentation


  • 610 Views
  • Uploaded on

Electromagnetic Blood Flow Meter Dr. Erdem Topsakal, Advisor Brian McCalebb Taffa Porter Kyle Eubanks Nashlie Sephus. Outline. Problem Statement Solution Introduction/Historical Information Technical Constraints Practical Constraints

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Electromagnetic Blood Flow Meter Dr. Erdem Topsakal, Advisor Br' - paul2


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Electromagnetic

Blood Flow Meter

Dr. Erdem Topsakal, Advisor

Brian McCalebb Taffa Porter Kyle Eubanks Nashlie Sephus


Outline l.jpg
Outline

  • Problem Statement

  • Solution

  • Introduction/Historical Information

  • Technical Constraints

  • Practical Constraints

  • Design Approaches/Tradeoffs

    - Testing Apparatus

    - Calibration

    - Probe

    - Electronics

  • Timeline

  • References


Problem l.jpg
Problem

  • The electromagnetic blood flow meters were originally used by the University of Mississippi Medical Center.

  • Obtaining replacements is no longer possible.

  • Other commercially available flow meters proved inadequate.


Solution l.jpg
Solution

  • Reproduce and improve the original probe

  • Reproduce similar results to the original meter

  • Minimum Cost

  • Dependable

  • Easy to use

  • Obtain accurate results


Slide5 l.jpg

Electromagnetic Blood Flow Meter

  • What Are Flow Meters?

  • Electromagnetic blood flow meters measure blood

    flow in blood vessels

  • Consists of a probe connected to a flow sensor box


Electromagnetic blood flow meter l.jpg
Electromagnetic Blood Flow Meter

  • Why They Are Used?

  • Offers quantitative data during surgical

    operations

  • Provides a functional assessment of

    newly joined vessels, grafts and organs

  • Used in prosthesis in conjunction with

    cardiovascular surgical procedures

  • Most accurate results through both

    acute and chronic implants


Electromagnetic blood flow meter7 l.jpg
Electromagnetic Blood Flow Meter

How Do They Work?

  • Faraday's Law of Magnetic Induction

  • Liquid acts as a conductor

  • Voltage is induced directly related to the average flow velocity

  • “The faster the flow rate, the higher the voltage”

  • Voltage is measured by sensing electrodes mounted in the meter tube

  • Voltage is then sent to the

    flow sensor box


Outline8 l.jpg
Outline

  • Problem Statement

  • Solution

  • Introduction/Historical Information

  • Technical Constraints

  • Practical Constraints

  • Design Approaches/Tradeoffs

    - Testing Apparatus

    - Calibration

    - Probe

    - Electronics

  • Timeline

  • References



Measurement accuracy l.jpg
Measurement Accuracy

  • Affected by:

    - Stray magnetic fields detected by electrodes

    - Non-uniform magnetic field

    - Turbulent fluid flow

    - Non-homogenous fluid

  • Accurate to within ±1 cm/s from 0.1-1 m/s

    - 10% maximum error at 0.1 m/s

    - 1% maximum error at 1 m/s


Maximum fluid velocity l.jpg
Maximum Fluid Velocity

  • Fluid velocities in an aorta

    - 89±9.5 cm/s during heart contraction

    - 36±6.0 cm/s between contractions

  • Fluid velocity for flow meter

    - 1 m/s maximum

  • Importance of low maximum fluid velocity

    - Maximizes accuracy for low fluid velocities by

    allowing more precision in A/D conversion


Conductivity l.jpg
Conductivity

  • Calibrated conductivity range

    • Conductivity of blood

      - 70 Siemens per centimeter

      - Varies by up to 20% based on flow rate

    • Acceptable conductivity range of flow meter

      - 60–80 Siemens per centimeter


Slide13 l.jpg
Size

  • Probe Size

    • 22 mm inner diameter

    • Reasoning

      - Requested by sponsor

      - Diameter of aorta ranges from 21-35 mm

      - Larger aortas taper down to smaller diameters



Sustainability l.jpg
Sustainability

  • Implanted for 2-3 months

  • Protection of wire leads, magnetic core, & wire coil

  • Maintenance of electrodes


Ethical l.jpg
Ethical

  • Designed for cow’s aorta only

  • Not approved or tested for human use


Outline17 l.jpg
Outline

  • Problem Statement

  • Solution

  • Introduction/Historical Information

  • Technical Constraints

  • Practical Constraints

  • Design Approaches/Tradeoffs

    - Testing Apparatus

    - Calibration

    - Probe

    - Electronics

  • Timeline

  • References





Slide21 l.jpg

Testing Apparatus

  • Via Aqua 1800 - $25.00

    - 480 GPH, variable flow rate

    - 3/4” connections

    - Saltwater safe

  • Acrylic tubing - $3.32 / 6ft.

    - 7/8” OD, 3/4” ID, 1/16” thickness

    - Insulating material


Slide22 l.jpg

Testing Apparatus

  • Dialysis tubing - $5.25 / 10ft

    - Will be used in future testing

    - 22 mm diameter

    - 1 mil thickness

    - Closely replicates the conductivity of an aorta

    - May use multiple layers to adjust the conductivity or increase the water pressure it can withstand


Calibration l.jpg
Calibration

  • Calibration and error can be minimized by selecting the proper voltage source waveform

    • DC

      - Voltage drift from polarization of electrodes

    • Sinusoidal AC

      - Reduces voltage drift by changing polarity

      - Induces emf in electrodes from magnetic flux variation

    • Square-wave AC

      - Reduces voltage drift by changing polarity

      - Reduces emf in electrodes from magnetic flux variation


Slide24 l.jpg

Calibration

  • Why does the output voltage of the probe not directly correlate to the fluid velocity?

    • Ideally, they are directly proportional

    • However, sources of error include:

      - Stray magnetic fields picked up by electrodes

      - Resistive and capacitive current leakage

      - Voltage loss through tubing

      - Voltage drift

      - Noise


Calibration25 l.jpg
Calibration

  • Fundamentals of Calibration

    • Under no flow conditions

      - Voltage observed is the combination of all sources of error since no voltage from fluid flow

    • Zero the output waveform

      - Cancels out all unwanted voltage contributions

      - Output now has a zero baseline voltage

    • Output voltage is now directly proportional to the fluid velocity


Calibration26 l.jpg
Calibration

  • Procedure

    - The most correct solution is to subtract the entire unwanted waveform

    - Requires unnecessary computations

    - Sampling occurs at the same place every cycle

    - Under no flow, calculate the average voltage at the

    desired sampling location for every cycle over some

    period

    - Subtracting this voltage for every sample gives the voltage contribution due to fluid velocity alone


Outline27 l.jpg
Outline

  • Problem Statement

  • Solution

  • Introduction/Historical Information

  • Technical Constraints

  • Practical Constraints

  • Design Approaches/Tradeoffs

    - Testing Apparatus

    - Calibration

    - Probe

    - Electronics

  • Timeline

  • References


Probe l.jpg
Probe

Key components

  • Magnetic core

  • Magnet wire

  • Electrodes


Probe29 l.jpg
Probe

  • Magnetic cores

    • Permeability

      - Describes how much a material is affected by magnetic fields and how strong a field it can generate

    • High permeability results in:

      - A stronger magnetic field


Probe30 l.jpg
Probe

  • Magnetic cores


Probe31 l.jpg
Probe

  • Magnet wire

    Key factors

    - Thin

    - Well-insulated

    - Close to range of 34 gauge (commonly used in industrial electromagnetic blood flow meters)

    - Availability

    - Low cost


Probe32 l.jpg
Probe

  • Electrodes

    Desirable qualities

    • Low resistance

      - More sensitive

    • High capacitance

      - Reduces source impedance and signal attenuation


Electrodes capacitance l.jpg
Electrodes - Capacitance

Platinized Platinum

Capacitance (µF)

Frequency (Hz)


Electrodes resistance l.jpg
Electrodes - Resistance

Resistance (kΩ)

Platinized Platinum

Frequency (Hz)



Electronics l.jpg
Electronics

Flow sensor box



References l.jpg
References

[1] Shercliff, J.A., The Theory of Electromagentic Flow-Measurement. Cambridge: University Press, 1962,pp. 2-4, 125.

[2] Flowmeter Directory. Flowmeter Directory. 2007.

http://www.flowmeterdirectory.com/flowmeter_electromagnetic.html

[3] Tavoularis, S., Measurement in Fluid Mechanics. Cambridge: University Press, 2005, pp. 217.

[4] Omega Engineering. Omega Engineering. 2006. http://www.omega.com/techref/flowcontrol.html

[5] EesiFlo. Eesiflo. 2007. http://www.eesiflo.com/applications.html

[6] Braun, U., and vetJosef, F., “Duplex ultrasonography of the common carotid artery and

external jugular vein of cows,” American Journal of Veterinary Research, vol. 66, no. 6,

pp.962-965, 2005.

[7] Khan, S. R., and Islam, M. N., “Studies on the prospect of bioprostheses by cow aortic valve for human use,” Bangladesh Med Res Counc Bull, vol. 17, no. 2, pp. 75-80, 1991.

[8] Wyatt, D. G., and Phil, D., "Problems in the Measurement of Blood Flow by

Magnetic Induction," Phys. Med. Biol., vol. 5, pp. 369-399, 1961.


ad