where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

585 views
Technical Discussions
Harris Goodyear
Harris Goodyear
06:56 Aug-16-2001
eddy current probe size

My question is why do you get great depth of penetration with a large diameter probe. The reason I ask this question is becauseif you increase your probe size in fact you increase your coil inductance, with more inductance you have more XL, more XL moves you down the conductivity curve. If you use your standard depth of penetration formula, the further down the conductivity curve you go your effective depth of penetration decreases, so how in fact can you get such great penetration. ALL the eddy current formulas contradict this coil size to great penetration theory.


    
 
 
Jeff Draper
Jeff Draper
04:28 Aug-17-2001
Re: eddy current probe size
I think you are mixing up your technical information. You seem to be combining the probe design properties with the material properties. You calculate standard depth of penetration for a given material you are testing, not for the probe. The impedance change related to increased inductance is for the probe, not the material, whereas the conductivity curve is for materials, not the probe.

If you take a look at the formula for calculating the standard depth of penetration on a given material, you will notice that inductance is not part of the equation. It depends only upon the material properties (conductivity & permeability) and the frequency at which you are driving the probe.

The formula is d=50*sqrt[r/(f*rp)]
d=depth of penetration in mm
r=resistivity in milliohm-cm (equal to 172.41/%IACS) f=frequency in Hz
rp=relative permeability

The only way inductance is remotely related to this equation is through the impedance matching of the probe and the bridge. This will give you your optimal operational frequency range for a given inductance with a given bridge impedance.



    
 
 
Avi Sela
Avi Sela
09:08 Jun-20-2002
Re: eddy current probe size
I think you are mixing up your technical information. You seem to be combining the probe design properties with the material properties. You calculate standard depth of penetration for a given material you are testing, not for the probe. The impedance change related to increased inductance is for the probe, not the material, whereas the conductivity curve is for materials, not the probe.
.
: If you take a look at the formula for calculating the standard depth of penetration on a given material, you will notice that inductance is not part of the equation. It depends only upon the material properties (conductivity & permeability) and the frequency at which you are driving the probe.
.
: The formula is d=50*sqrt[r/(f*rp)]
: d=depth of penetration in mm
: r=resistivity in milliohm-cm (equal to 172.41/%IACS) f=frequency in Hz
: rp=relative permeability
.
: The only way inductance is remotely related to this equation is through the impedance matching of the probe and the bridge. This will give you your optimal operational frequency range for a given inductance with a given bridge impedance.
.



    
 
 
Tomasz Piech
Tomasz Piech
09:36 Jun-20-2002
Re: eddy current probe size
: I think you are mixing up your technical information. You seem to be combining the probe design properties with the material properties. You calculate standard depth of penetration for a given material you are testing, not for the probe. The impedance change related to increased inductance is for the probe, not the material, whereas the conductivity curve is for materials, not the probe.
: .
: : If you take a look at the formula for calculating the standard depth of penetration on a given material, you will notice that inductance is not part of the equation. It depends only upon the material properties (conductivity & permeability) and the frequency at which you are driving the probe.
: .
: : The formula is d=50*sqrt[r/(f*rp)]
: : d=depth of penetration in mm
: : r=resistivity in milliohm-cm (equal to 172.41/%IACS) f=frequency in Hz
: : rp=relative permeability
: .
: : The only way inductance is remotely related to this equation is through the impedance matching of the probe and the bridge. This will give you your optimal operational frequency range for a given inductance with a given bridge impedance.
: .
.

Diese Formel ist d.h. Küche Formel", sie ist Viel zu vereinfacht. In der Tat muß man die Umrechnungen mit Hilfe sehr komplizierten (Besselschen Funktionen höherer Ordnung) berechnen. In der Ingenieurpraxis nimmt man nicht in der Acht, daß der Werkstoff stell sich als nichtlineares Material sondern linear. Magnetisch Permäabilität ist eine nichtlineare Funktion der Magnetfeldstärke und für aller Berechnungen soll man genaue Verteilung drr magnetischen Feldes zu kennen. Aber das zur Zeit unmöglich ist!


    
 
 
Tomasz Piech
Tomasz Piech
09:37 Jun-20-2002
Re: eddy current probe size
: I think you are mixing up your technical information. You seem to be combining the probe design properties with the material properties. You calculate standard depth of penetration for a given material you are testing, not for the probe. The impedance change related to increased inductance is for the probe, not the material, whereas the conductivity curve is for materials, not the probe.
: .
: : If you take a look at the formula for calculating the standard depth of penetration on a given material, you will notice that inductance is not part of the equation. It depends only upon the material properties (conductivity & permeability) and the frequency at which you are driving the probe.
: .
: : The formula is d=50*sqrt[r/(f*rp)]
: : d=depth of penetration in mm
: : r=resistivity in milliohm-cm (equal to 172.41/%IACS) f=frequency in Hz
: : rp=relative permeability
: .
: : The only way inductance is remotely related to this equation is through the impedance matching of the probe and the bridge. This will give you your optimal operational frequency range for a given inductance with a given bridge impedance.
: .
.

Diese Formel ist d.h. Küche Formel", sie ist Viel zu vereinfacht. In der Tat muß man die Umrechnungen mit Hilfe sehr komplizierten (Besselschen Funktionen höherer Ordnung) berechnen. In der Ingenieurpraxis nimmt man nicht in der Acht, daß der Werkstoff stell sich als nichtlineares Material sondern linear. Magnetisch Permäabilität ist eine nichtlineare Funktion der Magnetfeldstärke und für aller Berechnungen soll man genaue Verteilung drr magnetischen Feldes zu kennen. Aber das zur Zeit unmöglich ist!
mei e-mail war unkorrekt!
Richtig: piech@arcadia.tuniv.szczecin.pl

Bitte um Entschuldigung!


    
 
 

Product Spotlight

Ultrasonic Flaw Detector & Thickness Gauge: Smartor

SIUI’s newly launched Smartor is a combination of ultrasonic testing and ultrasonic thickness me
...
asurement. ●IP 66 ●Compact size: 198 (W)* 128 (H) *520 (D) mm ●0.9kg only with battery ●5.7" LCD with high resolution 640×480 pixels ●One-hand operation ●Multiple conventional UT functions ●Smart Test Wizard ●Weld Simulation
>

NDT.net launches mobile-friendly design

NDT.net has revamped its website providing a mobile-friendly design.The front page received a comp
...
letely new design and all other sections are now reacting responsively on mobile devices. This has been a major step to make our website more user- friendly.
>

GEKKO, Standard and Advanced phased-array for Easier inspection

With a 64-channel parallel architecture, GEKKO is a flaw detector offering at the same time conven
...
tional UT, standard PAUT, TOFD and real-time Total Focusing Method (TFM). GEKKO improves the detection, with better defects characterization and sizing as well as for misoriented defects. Some procedures require standard UT, others TOFD or PA. GEKKO includes all these techniques to offer a versatile and field-ready equipment. - 64:64 parallel channels - + 4 additional TOFD - Conventional UT channels - International code compliance: ASME, AWS, API, ASTM, ISO-EN Watch the video: https://youtu.be/kuEY_RwWS3Q
>

High-performance Linear Phased Array Probes

Available to order from stock in a range of 5MHz – 7.5MHz and from 16 to 64 elements. Designed w
...
ith piezo-composite elements, Phoenix phased array probes provide high-resolution imaging to maximise sensitivity; accurate ultrasonic detection and sizing of defects in welds; and effective corrosion mapping. Housed in a rugged stainless steel case for on-site industrial NDT applications.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window