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Technical Discussions
Dhiliban
Other, QA/QC engineer
L&T HCP, India, Joined May 2016, 16

Dhiliban

Other, QA/QC engineer
L&T HCP,
India,
Joined May 2016
16
10:17 Jun-20-2016
Dead Zone calculation

There is always a minimum thickness for any particular UT setup where the results are not sensitive,which is behalf of the interference effect close to the transducer,which we call as dead zone
How to calculate the dead zone

If somewhere i am wrong in my concept please rectify me

Thanks to you all in advance

    
 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 701

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
701
11:42 Jun-20-2016
Re: Dead Zone calculation
In Reply to Dhiliban at 10:17 Jun-20-2016 (Opening).

There is no calculation. You just have to measure it.

    
 
 
massimo carminati
Consultant, AUT specialist
IMG Ultrasuoni Srl, Italy, Joined Apr 2007, 691

massimo carminati

Consultant, AUT specialist
IMG Ultrasuoni Srl,
Italy,
Joined Apr 2007
691
23:08 Jun-20-2016
Re: Dead Zone calculation
In Reply to Dhiliban at 10:17 Jun-20-2016 (Opening).

The dead zone of a UT measuring chain and test condition has to be measured and is the minimum distance from beam entry point where an echo can be distinguished.

1    
 
 
Satyajeet Jena
Satyajeet Jena
08:54 Aug-03-2018
Re: Dead Zone calculation
In Reply to massimo carminati at 23:08 Jun-20-2016 .

It is a short time at which the transmitted signal blinds the received signal due to high noise of the crystal. Just like eye blinking. Happens in probe which transmit & receive in one crystal..

Thanks

    
 
 
langtuteng
Armenia, Joined Nov 2014, 155

langtuteng

Armenia,
Joined Nov 2014
155
03:45 Aug-05-2018
Re: Dead Zone calculation
In Reply to Dhiliban at 10:17 Jun-20-2016 (Opening).

Yes, the dead zone is measured. it is based on your probe, equipment and sensitivity. and it varies from different sensitivity. so I suggest you to measure it under the probe and equipment combined system, also with the sensitivity. the dead zone is the distance where you can distinguish the first echo behined the initial pulse echo, and mostly we define if the trough between the initial pulse wave and first echo wave is 6dB lower than the peak of first echo wave , then we can distiguish them and this diatance is dead zone.

2    
 
 
Arman
Engineering,
Turkey, Joined Oct 2014, 37

Arman

Engineering,
Turkey,
Joined Oct 2014
37
08:48 Aug-05-2018
Re: Dead Zone calculation
In Reply to massimo carminati at 23:08 Jun-20-2016 .

Gents,

Thanks for all explanations, could you please explain effect of parameters like probe frequency, crystal diameter ...etc on length of deadzone?

    
 
 
Paul Holloway
Consultant, UT Level 3
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 169

Paul Holloway

Consultant, UT Level 3
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
169
10:39 Aug-05-2018
Re: Dead Zone calculation
In Reply to Arman at 08:48 Aug-05-2018 .

There was a lengthy discussion regarding dead zone here:

https://www.ndt.net/forum/thread.php?msgID=62184

A simple forum orGoogle search would have revealed this.

    1
 
 

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