Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
1
Design of a Remote Electrical Conductivity
Measurement Sensor Based on Pulsed
Eddy Current Technology
Ehsan Shameli, Ph.D, P.Eng.
Senior Associate February 2012
2
Who We Are
Exponent is a multi-disciplinary consulting firm
dedicated to solving important science, engineering and
regulatory issues
for clients
3
Masters
30%
Doctorates
54%
Bachelors
16%
Consulting Staff
4
Harrogate
Derby
Düsseldorf Hangzhou
Boston: Maynard
Natick
Winchester Chicago: Lisle
Wood Dale Denver
Detroit
Houston
Miami
New York
Philadelphia
Phoenix
Seattle
Southern California: Irvine
Los Angeles
Washington, DC: District of Columbia
Maryland
Virginia
San Francisco Bay Area: Menlo Park
Oakland
Basel
Exponent Offices
5
6
Emerging Opportunities
Defense
Technology
Development
Design Support
Energy
Health
Transportation
Safety
7
Overview
Introduction of Eddy Current Testing
Pulsed Eddy Currents
Principal of Operation
Design Principles
Experimental Results
Conclusion
8
Current State of the Art
Continuous Eddy Current Testing Works based on principles of electromagnetic induction
Uses a continuous, sinusoidal excitation signal
Applications Defect detection
Monitoring heat and surface treatment
Alloy characterization and material sorting
Disadvantages Narrow band signal
High sensitivity to lift-off distance
Low penetration depth into the test targets
Thermal drift
High power consumption
9
Pulsed Eddy Current Testing
10
Pulsed Eddy Current
Wide band signals with more information
Deeper penetration into the test sample
Insensitive to lift-off distance
Energy efficiency
Less thermal drift
11
Applications of PE Technique
Conductivity measurement of objects
Thick layer of coating
Measurement targets with elevated temperatures
Molten metals
Measurements through conductive layers
12
Theoretical Principle
L
Din
Dout
dl
I
R
P(R)
Biot-Savart Law
13
Define coil aspect ratios
Calculate the current as a function of power supplied to the coil
Substitute the calculated current in the field equation
Collect all the geometry related terms into a geometry factor
Select optimal aspect ratios that maximize
Using the selected aspect ratios, select the inner diameter
Design Procedure – Driver Coil
Geometry
Factor
14
Driver Coil Design – Selection of Aspect Ratios
15
Considerations for Selection of and
Larger and smaller increase the field amplitude
Increasing the will grow the sensing footprint of the
transducer
Decreasing the makes the coil very thin and structurally
compromised
Larger coils have higher inductive and capacitive resistance
and slower dynamics
16
Driver Coil Design – Selection of Inner Diameter
Electric Current
Limitation Zone
17
Receiver Coil Geometry
S. Tumanski, “Induction Coil Sensors – a Review”
18
Receiver Coil Design
0.37 ( l=2.4 Di )
19
Experimental Setup
Driver Receiver
• Max. Lift-off Distance: 65mm
• Test Targets: Aluminum and
Copper sheets
• Coil Separation: 50mm
20
Driver and Pickup Signals
21
Signal Characteristics
23%
Signal Statistics – 500 Cycles of Measurement
Material Aluminum Copper
Normalized mean of maximum signal amplitude 1.00 0.667
Normalized STD of maximum signal amplitude
0.0098 0.0146
22
Summary
A Remote Conductivity Measurement System was designed and
prototyped
The system can operate at lift-off distance up to 65mm
There is a 23% contrast between the signal levels obtained from
aluminum and copper samples
Standard deviation of measurements is less than 2.5%
23
Thanks