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 -
722 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.


 
 Reply 
 
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.



 
 Reply 
 
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.
.



 
 Reply 
 
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!


 
 Reply 
 
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!


 
 Reply 
 

Product Spotlight

NEW! The PragmaPro Instrument Platform

The PragmaPro is based on a modular cartridge technology and supports various NDT instrument modal
...
ities such as UT, PAUT, ECT and many more. This new platform is based on a machined, powder-coated aluminum frame for shock-proofness, best sealing qualities and maximum heat dissipation. This is practical to extend the outdoor temperature range and/or to extend the power injected in the transducers. The PragmaPro is aiming at a very wide range of applications, such as weld scanning, corrosion mapping and composite testing.
>

IRIS 9000Plus - Introducing the next generation of heat exchanger inspection.

Representing the seventh generation of the IRIS system, the IRIS 9000 Plus has nearly 200 years of c
...
ombined field inspection experience incorporated in its design. This experience combined with a strong commitment to quality and a history of innovation has made Iris Inspection Services® the undisputed leader in IRIS technology.
>

Immersion systems

ScanMaster ultrasonic immersion systems are designed for high throughput, multi shift operation in a
...
n industrial or lab environment. These fully integrated systems provide various scanning configurations and incorporate conventional and phased arrays technologies to support diverse applications, such as inspection of disks, bars, shafts, billets and plates. All of ScanMaster immersion systems are built from high accuracy scanning frames allowing for scanning of complex parts and include a multi-channel ultrasonic instrument with exceptional performance. The systems are approved by all major manufacturers for C-scan inspection of jet engine forged discs. Together with a comprehensive set of software modules these flexible series of systems provide the customer with the best price performance solutions.
>

EKOSCAN Phased Array

In order to always fit your needs, EKOSCAN can manufacture any type of UT transducer, either convent
...
ional or Phased Array. As an ISO 9001: 2015 certified company, EKOSCAN is extremely careful as far a material selection and manufacturing processes are concerned. Our probes guarantee our customers the benefits of latest innovations regarding piezo-composite, backing, impedance adaptation layer, etc. Specific probes for hostile environment: high temperature, high pressure, corrosive environment,etc. Specific probes designed to fit your specific application: optimization of every parameter to guarantee you the best detection.
>

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