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- since 1996 -

AT-Automation Technology GmbH
AT -Automation Technology is a systems house for industrial image processing. AT offers thermographic ndt systems as well as high-speed 3D sensors.
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Technical Discussions
Sumit
NDT Inspector, (Phased Array & ToFD)
India, Joined Jan 2011, 21

Sumit

NDT Inspector, (Phased Array & ToFD)
India,
Joined Jan 2011
21
11:29 Apr-10-2013
ELECTRICAL NOISE IN TOFD

Dear all

I am using Omniscan MX equipment for a TOFD inspection. Sometimes I am getting lots of electrical noise.

Is there any solution for this ?

Thanks

 
 Reply 
 
Billy
Billy
11:33 Apr-10-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Sumit at 11:29 Apr-10-2013 (Opening).

Turn the power off anything close by or that is connected to what you're inspecting.

Make sure all cables are OK.

 
 Reply 
 
sumit
NDT Inspector, (Phased Array & ToFD)
India, Joined Jan 2011, 21

sumit

NDT Inspector, (Phased Array & ToFD)
India,
Joined Jan 2011
21
14:08 Apr-10-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Billy at 11:33 Apr-10-2013 .

Nothing is connected to the job. All cables are also in good condition.

I heard about low noise co axial cables. Is there anything like that in market which can reduce electrical noise ?

 
 Reply 
 
Mark Nel
Sales, Application support
Technology Design Ltd., United Kingdom, Joined Jul 2005, 58

Mark Nel

Sales, Application support
Technology Design Ltd.,
United Kingdom,
Joined Jul 2005
58
16:34 Apr-10-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to sumit at 14:08 Apr-10-2013 .

Hi Sumit, ToFD is notorious for its propensity to be noisy. Unfortunately it is not always easy to track down or even control the source of the noise. Noise may be generated by any number of obscure sources like welding operation elsewhere in the plant that may be somehow connected to the item you are inspecting, if you are testing a vessel on rollers, these are notoriously noisy, electric motors and pumps in the vicinity and so on, the list is endless. I did a job in Pakistan many years ago where during the day it was impossible to collect usable ToFD data but at exactly 10PM every night the baseline became perfectly flat and the data was excellent, then at exactly 5AM the noise started again. We never did find the source.

As Billy said do all the obvious things first, like checking that the connectors are screwed in tightly, cables, use a pre-amp to clean up the signal a little, if you are using plant power instead of the unit's own batteries then use a UPS as well, try signal averaging if this unit has this function and so on. Be very sure that the cables are correctly attached to the connectors because even a single strand of misplaced shielding wire can cause noise if the cable is bent in a certain direction and shorts across the connector. This may all sound a little pedantic but take it from someone who has spent thousands of hours doing ToFD in some pretty horrible conditions that it is often the small details that make all the difference to good or bad data and consequently your piece of mind.
Good luck on the job.

1
 
 Reply 
 
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
12:21 Apr-11-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Sumit at 11:29 Apr-10-2013 (Opening).

The problem is that the pulser /receiver of the Omniscan requires the use of a remote preamplifier. This will solve most of the environmental interferences you are experimenting. We have a battery operated remote preamp 40 db with a certified bandwith up to 20 MHz @ -3 dB. We normally have these in stock. Feel free to contact us at img@img-us.com

 
 Reply 
 
Abbas Bombaywala
NDT Inspector
Free Lance, India, Joined Jul 2007, 92

Abbas Bombaywala

NDT Inspector
Free Lance,
India,
Joined Jul 2007
92
12:15 Apr-16-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Sumit at 11:29 Apr-10-2013 (Opening).

I know this will sound little wierd but i actually use to do this. Take a copper wire and attach one end to the scanner and other end to the earthing cable nearby. I use to do this when I use Sonovision Equipment and I could easily collect the Data even during Welding work was carried out at the other parts of the vessel.

With Omni Scan dont use it with Powersupply from the plant use it on the batteries, try to shoreten the lenght of the cables, try using preamplifier, or else last soultion is try using a better equipment which can provide u with better averaging which will reduce your electrical noise.

Regards.

1
 
 Reply 
 
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
21:03 Apr-16-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Abbas Bombaywala at 12:15 Apr-16-2013 .

You are right, grounding may help too.

 
 Reply 
 
Radoslaw
NDT Inspector, Materials Engineer
Poland, Joined Apr 2012, 51

Radoslaw

NDT Inspector, Materials Engineer
Poland,
Joined Apr 2012
51
20:46 Apr-17-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to massimo carminati at 21:03 Apr-16-2013 .

Problem with noise.

For AUT testing I use CRC equipment (trolley+traveling band) and I have some noise (TOFD) from the motor of this trolley. How could I fix this problem?

 
 Reply 
 
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
06:18 Apr-19-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to Radoslaw at 20:46 Apr-17-2013 .

Same comments (use remote preamps and grounding). In addition, you should know which motors you are using. Steppers can be very noisy, as an example. Double shield the umbelical cable of the probes and keep as far as possible from it the motors cabling.

 
 Reply 
 
Wieslaw Bicz
Engineering,
PBP Optel sp. z o.o., Poland, Joined Feb 2009, 266

Wieslaw Bicz

Engineering,
PBP Optel sp. z o.o.,
Poland,
Joined Feb 2009
266
11:39 Apr-19-2013
Re: ELECTRICAL NOISE IN TOFD
In Reply to massimo carminati at 06:18 Apr-19-2013 .

You are fully correct informing about noisy stepper motors. I will only add, that this noise can be significantly limited if proper controller is used. But it is not so easy to find a controller with suitable properties. We have for example developed for our scanners a special controller, that is generating very small amount of noise and creating a very smooth movement. But it was necessary to use discrete elements for end stage of this device and quite sophisticated current control.

 
 Reply 
 

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